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Sample records for microwave heating obtencao

  1. Heat transfer in microwave heating

    NASA Astrophysics Data System (ADS)

    Peng, Zhiwei

    Heat transfer is considered as one of the most critical issues for design and implement of large-scale microwave heating systems, in which improvement of the microwave absorption of materials and suppression of uneven temperature distribution are the two main objectives. The present work focuses on the analysis of heat transfer in microwave heating for achieving highly efficient microwave assisted steelmaking through the investigations on the following aspects: (1) characterization of microwave dissipation using the derived equations, (2) quantification of magnetic loss, (3) determination of microwave absorption properties of materials, (4) modeling of microwave propagation, (5) simulation of heat transfer, and (6) improvement of microwave absorption and heating uniformity. Microwave heating is attributed to the heat generation in materials, which depends on the microwave dissipation. To theoretically characterize microwave heating, simplified equations for determining the transverse electromagnetic mode (TEM) power penetration depth, microwave field attenuation length, and half-power depth of microwaves in materials having both magnetic and dielectric responses were derived. It was followed by developing a simplified equation for quantifying magnetic loss in materials under microwave irradiation to demonstrate the importance of magnetic loss in microwave heating. The permittivity and permeability measurements of various materials, namely, hematite, magnetite concentrate, wüstite, and coal were performed. Microwave loss calculations for these materials were carried out. It is suggested that magnetic loss can play a major role in the heating of magnetic dielectrics. Microwave propagation in various media was predicted using the finite-difference time-domain method. For lossy magnetic dielectrics, the dissipation of microwaves in the medium is ascribed to the decay of both electric and magnetic fields. The heat transfer process in microwave heating of magnetite

  2. Variable frequency microwave heating apparatus

    DOEpatents

    Bible, Don W.; Lauf, Robert J.; Johnson, Arvid C.; Thigpen, Larry T.

    1999-01-01

    A variable frequency microwave heating apparatus (10) designed to allow modulation of the frequency of the microwaves introduced into a multi-mode microwave cavity (34) for testing or other selected applications. The variable frequency microwave heating apparatus (10) includes a microwave signal generator (12) and a high-power microwave amplifier (20) or a high-power microwave oscillator (14). A power supply (22) is provided for operation of the high-power microwave oscillator (14) or microwave amplifier (20). A directional coupler (24) is provided for detecting the direction and amplitude of signals incident upon and reflected from the microwave cavity (34). A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load (28).

  3. Variable frequency microwave heating apparatus

    SciTech Connect

    Bible, D.W.; Lauf, R.J.; Johnson, A.C.; Thigpen, L.T.

    1999-10-05

    A variable frequency microwave heating apparatus (10) designed to allow modulation of the frequency of the microwaves introduced into a multi-mode microwave cavity (34) for testing or other selected applications. The variable frequency microwave heating apparatus (10) includes a microwave signal generator (12) and a high-power microwave amplifier (20) or a high-power microwave oscillator (14). A power supply (22) is provided for operation of the high-power microwave oscillator (14) or microwave amplifier (20). A directional coupler (24) is provided for detecting the direction and amplitude of signals incident upon and reflected from the microwave cavity (34). A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. Reflected power is dissipated in the reflected power load (28).

  4. [Microwave-induced heating injury].

    PubMed

    Frey, F J

    2004-12-01

    The case reported herein involves burns at the lower extremities leading to amputation followed by an MRSA infection with subsequent myocardial infarction and death in a patient with diabetes on chronic ambulatory peritoneal dialysis. The burns were produced by the use of a warm-up pillow containing natural stones (grape seeds) heated by microwaves. This represents another of the strange potential hazards of serious microwave related injuries.

  5. Microwave heating of porous media

    SciTech Connect

    Gori, F.; Martini, L. ); Gentili, G.B. )

    1987-05-01

    The technique actually used for recycling in place asphaltic concrete pavements is the following: heating of the surface layer of the pavement with special infrared lamps (gas-fed); hot removal and remixing in place of the materials with the addition of new binder; in-line reconstruction of the pavement layer with rolling. Such a technique is highly efficient and economic but it suffers an important disadvantage: The low thermal conductivity of the asphalt causes a strong temperature decrease with depth. Further on, the infrared radiation produces carbonization of the pavement skin with possible modification of the rheological properties of the bitumen. The technology of microwave generators (Magnetron, Klystron, and Amplitron) has registered some recent advances. It is now possible, and in some cases convenient, to use microwave energy for industrial heating of low-thermal-conductivity materials. Actually the microwaves are employed for drying wood, paper, and textiles, and for freeze-drying, cooking, and defrosting foods. One of the most interesting features of the microwave process is the rate and uniformity of the heating inside the material. Some preliminary experiments have been carried out for recycling in place asphaltic concrete pavements. The goal of the present paper is to propose a theoretical model capable of describing the phenomena occurring in a soil during a microwave heating process.

  6. Microwave heating apparatus and method

    DOEpatents

    Johnson, Andrew J.; Petersen, Robert D.; Swanson, Stephen D.

    1990-01-01

    An apparatus is provided for heating and melting materials using microwave energy, and for permitting them to solidify. The apparatus includes a microwave energy source, a resonant cavity having an opening in its floor, a microwave energy choke encompassing the opening in the floor of the cavity, a metal container to hold the materials to be heated and melted, a turntable, and a lift-table. During operation, the combined action of the turntable and the lift-table position the metal container so that the top of the container is level with the floor of the cavity, is in substantial registration with the floor opening, and is encompassed by the microwave energy choke; thus, during operation, the interior of the container defines part of the resonant cavity. Additionally, a screw feeder, extending into the cavity and sheltered from microwave energy by a conveyor choke, may convey the materials to be heated to the container. Also, preferably, the floor of the resonant cavity may include perforatins, so that the offgases and dust generated in the apparatus may be removed from the resonant cavity by pulling outside air between the container choke and the exterior wall of the container into the resonant cavity and out from the cavity through the perforations.

  7. Microwave heat treating of manufactured components

    DOEpatents

    Ripley, Edward B.

    2007-01-09

    An apparatus for heat treating manufactured components using microwave energy and microwave susceptor material. Heat treating medium such as eutectic salts may be employed. A fluidized bed introduces process gases which may include carburizing or nitriding gases. The process may be operated in a batch mode or continuous process mode. A microwave heating probe may be used to restart a frozen eutectic salt bath.

  8. Controlled Microwave Heating Accelerates Rolling Circle Amplification.

    PubMed

    Yoshimura, Takeo; Suzuki, Takamasa; Mineki, Shigeru; Ohuchi, Shokichi

    2015-01-01

    Rolling circle amplification (RCA) generates single-stranded DNAs or RNA, and the diverse applications of this isothermal technique range from the sensitive detection of nucleic acids to analysis of single nucleotide polymorphisms. Microwave chemistry is widely applied to increase reaction rate as well as product yield and purity. The objectives of the present research were to apply microwave heating to RCA and indicate factors that contribute to the microwave selective heating effect. The microwave reaction temperature was strictly controlled using a microwave applicator optimized for enzymatic-scale reactions. Here, we showed that microwave-assisted RCA reactions catalyzed by either of the four thermostable DNA polymerases were accelerated over 4-folds compared with conventional RCA. Furthermore, the temperatures of the individual buffer components were specifically influenced by microwave heating. We concluded that microwave heating accelerated isothermal RCA of DNA because of the differential heating mechanisms of microwaves on the temperatures of reaction components, although the overall reaction temperatures were the same.

  9. Microwave heating characteristics of magnetite ore

    NASA Astrophysics Data System (ADS)

    Rajavaram, Ramaraghavulu; Lee, Jaehong; Oh, Joon Seok; Kim, Han Gyeol; Lee, Joonho

    2016-11-01

    The heating characteristics of magnetite ore under microwave irradiation were investigated as a function of incident microwave power, particle size, and magnetite ore mass. The results showed that the heating rate of magnetite ore is highly dependent on microwave power and magnetite ore mass. The maximum heating rate was obtained at a microwave irradiation power of 1.70 kW with a mass of 25 g and particle size between 53-75 µm. The volumetric heating rate of magnetite ore was investigated by measuring the temperature at different depths during microwave irradiation. Microwave irradiation resulted in modification of the microstructure of the magnetite ore, but new phases such as FeO or Fe2O3 were not formed. In addition, the crystal size decreased from 115 nm to 63 nm after microwave irradiation up to 1573 K.

  10. Heating And Positioning In A Microwave Cavity

    NASA Technical Reports Server (NTRS)

    Jackson, Henry W.; Barmatz, Martin B; Watkins, John L.

    1994-01-01

    Two reports describe theoretical and experimental studies of microwave dielectrophoretic positioning of spherical sample of lossy dielectric material in microwave resonant cavity and heating of positioned sphere by electro-magnetic field. Studies part of continuing effort to develop techniques for containerless processing of materials in microgravity. Previous studies in this series described in "Microwave Dielectrophoretic Levitation in Microgravity" (NPO-18824).

  11. Modeling of microwave heating of particulate metals

    NASA Astrophysics Data System (ADS)

    Mishra, P.; Upadhyaya, A.; Sethi, G.

    2006-10-01

    Recent studies have shown that metal powder compacts can be heated to high temperatures using microwaves. While microwave heating of ceramics is well understood and modeled, there is still uncertainty about the exact mechanism and mode of microwave heating of particulate metals. The current study describes an approach for modeling the microwave heating of metal powder compacts using an electromagnetic-thermal model. The model predicts the variation in temperature with time during sintering. The effect of powder size, emissivity, and susceptor heating on the heating rate has also been assessed. These predictions have been validated by the experimental observations of the thermal profiles of Sn-, Cu-, and W-alloy compacts, using a 2.45 GHz multimode microwave furnace.

  12. Aspects of microwave-heating uniformity

    SciTech Connect

    Ginsberg, T.; Makowitz, H.

    1983-01-01

    Interest has been shown in the field of nuclear reactor safety in the use of microwave heating to simulate the nuclear heat source. The objective of the investigation reported here was to evaluate the usefulness of microwave dielectric heating as a simulator of the nuclear heat source in experiments which simulate the process of boiling of molten mixtures of nuclear fuel and steel. This paper summarizes the results of studies of several aspects of energy deposition in dielectric liquid samples which are exposed to microwave radiation.

  13. Automatic control during microwave heating of ceramics

    SciTech Connect

    Li, M.; Beale, G.O.; Tian, Yong Lai

    1995-12-31

    This paper presents results on the development of a feedback control system for regulating temperature in ceramic samples being heated by microwave energy for the purpose of joining. The main objective of the control system is to prevent thermal runaway in the ceramic samples during heating. Microwave power level and the positions of a movable iris and plunger are the variables being controlled. Results obtained from heating mullite and silicon carbide are presented. These results indicate the ability of the control system to prevent thermal runaway during microwave heating of the samples.

  14. Controlled Microwave Heating Accelerates Rolling Circle Amplification

    PubMed Central

    Yoshimura, Takeo; Suzuki, Takamasa; Mineki, Shigeru; Ohuchi, Shokichi

    2015-01-01

    Rolling circle amplification (RCA) generates single-stranded DNAs or RNA, and the diverse applications of this isothermal technique range from the sensitive detection of nucleic acids to analysis of single nucleotide polymorphisms. Microwave chemistry is widely applied to increase reaction rate as well as product yield and purity. The objectives of the present research were to apply microwave heating to RCA and indicate factors that contribute to the microwave selective heating effect. The microwave reaction temperature was strictly controlled using a microwave applicator optimized for enzymatic-scale reactions. Here, we showed that microwave-assisted RCA reactions catalyzed by either of the four thermostable DNA polymerases were accelerated over 4-folds compared with conventional RCA. Furthermore, the temperatures of the individual buffer components were specifically influenced by microwave heating. We concluded that microwave heating accelerated isothermal RCA of DNA because of the differential heating mechanisms of microwaves on the temperatures of reaction components, although the overall reaction temperatures were the same. PMID:26348227

  15. Modelling batch microwave heating of water

    NASA Astrophysics Data System (ADS)

    Yeong, S. P.; Law, M. C.; Lee, C. C. Vincent; Chan, Y. S.

    2017-07-01

    A numerical model of the microwave heating of distilled water is developed using COMSOL Multiphysics software to investigate the microwave effects on the heating rate. Three frequencies (0.915GHz, 2GHz and 2.45 GHz) have been applied in the model in order to study their influences on the water temperature. It is found that the water heats up at 2GHz and 2.45GHz, however, there is no sign of heating at 915MHz. This is supported with the figures of the electric field distribution in the microwave cavity. The results shown in the developed model is validated with the experimental results obtained at 2.45 GHz.

  16. Using Microwaves to Heat Lunar Soil

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin C.

    2011-01-01

    This slide presentation reviews the use of microwaves to heat lunar soil in order to obtain water. There appears to be large amounts of water in the lunar poles, in Martian areas in lower latitudes and some of the Moons of Jupiter. The presence of water in the south lunar polar region was demonstrated by the Lunar CRater Observation and Sensing Satellite (LCROSS) mission. Microwaves can be used to extract water from lunar soil without excavation. Using microwaves on a lunar soil simulant at least 95% of the water from the regolith permafrost simulant was extracted (2 minutes). The process is modeled using COMSOL Multiphysics Finite Element analysis microwave physics module and demonstrated usingan experiment of an microwave apparatus on a rover.

  17. Selection of biological indicator for validating microwave heating sterilization.

    PubMed

    Sasaki, K; Mori, Y; Honda, W; Miyake, Y

    1998-01-01

    For the purpose of selecting an appropriate biological indicator for evaluation of the effects of microwave heating sterilization, we examined aerobic bacterial spores to determine whether microwaves have non-thermal sterilization effects. After microwave irradiation on dry bacterial spores (three species), none of the bacterial spores were killed. The survival rate of the spores after microwave irradiation of spore suspensions (twelve species) was compared with that after heating by a conventional method. The order of heat resistance in the bacterial species was similar between the two heating methods. Bacillus stearothermophilus spores were the most heat-resistant. These results suggest that microwaves have no non-thermal sterilization effects on bacterial spores, the specific resistant spores to microwave heating, and microwave heating sterilization can be evaluated in the same way as for conventional heating sterilization. As a biological indicator for evaluation of overkill sterilization, B. stearothermophilus spores may be appropriate for microwave heating sterilization as well as steam sterilization.

  18. Hybrid microwave-cavity heat engine.

    PubMed

    Bergenfeldt, Christian; Samuelsson, Peter; Sothmann, Björn; Flindt, Christian; Büttiker, Markus

    2014-02-21

    We propose and analyze the use of hybrid microwave cavities as quantum heat engines. A possible realization consists of two macroscopically separated quantum-dot conductors coupled capacitively to the fundamental mode of a microwave cavity. We demonstrate that an electrical current can be induced in one conductor through cavity-mediated processes by heating up the other conductor. The heat engine can reach Carnot efficiency with optimal conversion of heat to work. When the system delivers the maximum power, the efficiency can be a large fraction of the Carnot efficiency. The heat engine functions even with moderate electronic relaxation and dephasing in the quantum dots. We provide detailed estimates for the electrical current and output power using realistic parameters.

  19. Apparatus for microwave heat treatment of manufactured components

    DOEpatents

    Ripley, Edward B.

    2008-04-15

    An apparatus for heat treating manufactured components using microwave energy and microwave susceptor material. Heat treating medium such as eutectic salts may be employed. A fluidized bed introduces process gases which may include carburizing or nitriding gases. The process may be operated in a batch mode or continuous process mode. A microwave heating probe may be used to restart a frozen eutectic salt bath.

  20. Methods for microwave heat treatment of manufactured components

    SciTech Connect

    Ripley, Edward B.

    2010-08-03

    An apparatus for heat treating manufactured components using microwave energy and microwave susceptor material. Heat treating medium such as eutectic salts may be employed. A fluidized bed introduces process gases which may include carburizing or nitriding gases. The process may be operated in a batch mode or continuous process mode. A microwave heating probe may be used to restart a frozen eutectic salt bath.

  1. Apparatus for microwave heat treatment of manufactured components

    DOEpatents

    Babcock & Wilcox Technical Services Y-12, LLC

    2008-04-15

    An apparatus for heat treating manufactured components using microwave energy and microwave susceptor material. Heat treating medium such as eutectic salts may be employed. A fluidized bed introduces process gases which may include carburizing or nitriding gases. The process may be operated in a batch mode or continuous process mode. A microwave heating probe may be used to restart a frozen eutectic salt bath.

  2. Glycerol citrate polyesters produced through microwave heating

    USDA-ARS?s Scientific Manuscript database

    The influence of various heating methods without catalysis to prepare copolyesters from citric acid:glycerol blends were studied. In the presence of short term microwave treatments, i.e., 60 sec at 1200 W, blends of glycerol and citric acid invariably formed solid amorphous copolyesters. Fourier tra...

  3. Effect of Microwave Heating on Phytosterol Oxidation.

    PubMed

    Leal-Castañeda, Everth Jimena; Inchingolo, Raffaella; Cardenia, Vladimiro; Hernandez-Becerra, Josafat Alberto; Romani, Santina; Rodriguez-Estrada, María Teresa; Galindo, Hugo Sergio García

    2015-06-10

    The oxidative stability of phytosterols during microwave heating was evaluated. Two different model systems (a solid film made with a phytosterol mixture (PSF) and a liquid mixture of phytosterols and triolein (1:100, PS + TAG (triacylglycerol))) were heated for 1.5, 3, 6, 12, 20, and 30 min at 1000 W. PS degraded faster when they were microwaved alone than in the presence of TAG, following a first-order kinetic model. Up to 6 min, no phytosterol oxidation products (POPs) were generated in both systems. At 12 min of heating, the POP content reached a higher level in PSF (90.96 μg/mg of phytosterols) than in PS + TAG (22.66 μg/mg of phytosterols), but after 30 min of treatment, the opposite trend was observed. 7-Keto derivates were the most abundant POPs in both systems. The extent of phytosterol degradation depends on both the heating time and the surrounding medium, which can impact the quality and safety of the food product destined to microwave heating/cooking.

  4. Microwave heating of lunar materials. Appendix A

    NASA Technical Reports Server (NTRS)

    Meek, Thomas T.

    1992-01-01

    Microwave heating of nonmetallic inorganic material has been of interest for many years. Von Hippel in the late 1940's and early 1950's investigated how microwave radiation up to 10 GHz couples to various insulator materials. Perhaps the most work has been done by Wayne Tinga at the University of Edmonton. Most of the work to date has been done at the two frequency bands allowed in industrial use (0.915 GHz and 2.45 GHz). However some work has recently been carried out at 28 GHz and 60 GHz. Work done in this area at Los Alamos National Laboratory is discussed.

  5. Review on Microwave-Matter Interaction Fundamentals and Efficient Microwave-Associated Heating Strategies.

    PubMed

    Sun, Jing; Wang, Wenlong; Yue, Qinyan

    2016-03-25

    Microwave heating is rapidly emerging as an effective and efficient tool in various technological and scientific fields. A comprehensive understanding of the fundamentals of microwave-matter interactions is the precondition for better utilization of microwave technology. However, microwave heating is usually only known as dielectric heating, and the contribution of the magnetic field component of microwaves is often ignored, which, in fact, contributes greatly to microwave heating of some aqueous electrolyte solutions, magnetic dielectric materials and certain conductive powder materials, etc. This paper focuses on this point and presents a careful review of microwave heating mechanisms in a comprehensive manner. Moreover, in addition to the acknowledged conventional microwave heating mechanisms, the special interaction mechanisms between microwave and metal-based materials are attracting increasing interest for a variety of metallurgical, plasma and discharge applications, and therefore are reviewed particularly regarding the aspects of the reflection, heating and discharge effects. Finally, several distinct strategies to improve microwave energy utilization efficiencies are proposed and discussed with the aim of tackling the energy-efficiency-related issues arising from the application of microwave heating. This work can present a strategic guideline for the developed understanding and utilization of the microwave heating technology.

  6. Graphene oxide reduction by microwave heating

    SciTech Connect

    Longo, Angela; Carotenuto, Gianfranco

    2016-05-18

    The possibility to prepare thermal reduced graphene oxide (Tr-GO) colloidal suspensions by microwave heating of graphene oxide (GO) suspensions in N-methyl-2-pyrrolidone (NMP) has been investigated. According to transmission electron microscopy (TEM) and absorption and emission spectroscopy characterization, such a type of thermal reduction does not lead to graphene quantum dots formation because only mono-functional oxygen-containing groups are removed.

  7. Review on Microwave-Matter Interaction Fundamentals and Efficient Microwave-Associated Heating Strategies

    PubMed Central

    Sun, Jing; Wang, Wenlong; Yue, Qinyan

    2016-01-01

    Microwave heating is rapidly emerging as an effective and efficient tool in various technological and scientific fields. A comprehensive understanding of the fundamentals of microwave–matter interactions is the precondition for better utilization of microwave technology. However, microwave heating is usually only known as dielectric heating, and the contribution of the magnetic field component of microwaves is often ignored, which, in fact, contributes greatly to microwave heating of some aqueous electrolyte solutions, magnetic dielectric materials and certain conductive powder materials, etc. This paper focuses on this point and presents a careful review of microwave heating mechanisms in a comprehensive manner. Moreover, in addition to the acknowledged conventional microwave heating mechanisms, the special interaction mechanisms between microwave and metal-based materials are attracting increasing interest for a variety of metallurgical, plasma and discharge applications, and therefore are reviewed particularly regarding the aspects of the reflection, heating and discharge effects. Finally, several distinct strategies to improve microwave energy utilization efficiencies are proposed and discussed with the aim of tackling the energy-efficiency-related issues arising from the application of microwave heating. This work can present a strategic guideline for the developed understanding and utilization of the microwave heating technology. PMID:28773355

  8. A container for heat treating materials in microwave ovens

    DOEpatents

    Holcombe, C.E.; Dykes, N.L.; Kimrey, H.D. Jr.; Mills, J.E.

    1988-01-26

    The efficiency of a microwave oven of a conventional two-source configuration and energy level is increased by providing the oven with a container for housing a refractory material to be treated. The container is formed to top and bottom walls transparent to microwaves while the sidewalls, in a circular configuration, are formed of a nonmetallic material opaque to microwave radiation for reflecting the radiation penetrating the top and bottom walls radially inwardly into the center of the container wherein a casket of heat-insulating material is provided for housing the material to be heat treated. The reflection of the microwave radiation from the sidewalls increases the concentration of the microwaves upon the material being heat treated while the concentration of the microwaves upon the material being heat treated while the casket retains the heat to permit the heating of the material to a substantially higher temperature than achievable in the oven without the container.

  9. Microwave radiometry for continuous non-contact temperature measurements during microwave heating.

    PubMed

    Stephan, Karl D; Pearce, John A

    2005-01-01

    Temperature measurement during microwave heating in industrial and commercial processes can improve quality, throughput, and energy conservation. Conventional ways of measuring temperature inside a microwave oven cavity are costly, inconvenient, or unsuitable for high-volume industrial applications. In this paper, we describe the theory of microwave radiometry as applied to the measurement of temperature during microwave heating. By extending the theory of radiative transfer to the case of thermal microwave radiation inside a cavity, we show that the same characteristics which make a microwave cavity suitable for heating materials also assist in obtaining meaningful temperature data with microwave radiometry. We present experimental data from the heating of liquid and solid materials which confirm the essential features of the theory, and show agreement between this method and more conventional methods of +/-4 degrees C.

  10. Microwave heating and current drive in tokamaks

    SciTech Connect

    Cohen, B.I.; Cohen, R.H.; Kerbel, G.D.; Logan, B.G.; Matsuda, Y.; McCoy, M.G.; Nevins, W.M.; Rognlien, T.D.; Smith, G.R.; Harvey, R.W.; Kritz, A.H.; Bonoli, P.T.; Porkolab, M.

    1988-08-23

    The use of powerful microwave sources provide unique opportunities for novel and efficient heating and current-drive schemes in the electron-cyclotron and lower-hybrid ranges of frequencies. Free- electron lasers and relativistic klystrons are new sources that have a number of technical advantages over conventional, lower-intensity sources; their use can lead to improved current-drive efficiencies and better penetration into a reactor-grade plasma in specific cases. This paper reports on modeling of absorption and current drive, in intense-pulse and quasilinear regimes, and on analysis of parametric instabilities and self-focusing. 16 refs., 2 figs.

  11. A New Automated Microwave Heating Process for Cooking and Pasteurization of Microwaveable Foods Containing Raw Meats

    USDA-ARS?s Scientific Manuscript database

    A new microwave heating process was developed for cooking microwaveable foods containing raw meats. A commercially available inverter-based microwave oven was modified for pasteurization of mechanically tenderized beef, inoculated with Escherichia coli O157:H7 (~ 5 log cfu/g) and packaged in a 12 o...

  12. Wood liquefaction with phenol by microwave heating and FTIR evaluation

    Treesearch

    Gaiyun Li; Chungyun Hse; Tefu Qin

    2015-01-01

    We examined wood liquefaction using phenol and mixed acid catalysts with microwave heating, and compared that with similar processes that use oil bath heating. The reaction time for microwave heating to achieve a residue content was one sixth, one eighteenth, and one twenty-fourth of that from oil bath heating, respectively, for phenol to wood (P/W) ratios of 2.5/1, 2/...

  13. Container for heat treating materials in microwave ovens

    DOEpatents

    Holcombe, Cressie E.; Dykes, Norman L.; Kimrey, Jr., Harold D.; Mills, James E.

    1989-01-01

    The efficiency of a microwave oven of a conventional two-source configuration and energy level is increased by providing the oven with a container for housing a refractory material to be treated. The container is formed of top and bottom walls transparent to microwaves while the sidewalls, in a circular configuration, are formed of a nonmetallic material opaque to microwave radiation reflecting the radiation penetrating the top and bottom walls radially inwardly into the center of the container wherein a casket of heat-insulating material is provided for housing the material to be heat treated. The reflection of the microwave radiation from the sidewalls increases the concentration of the microwaves upon the material being heat treated while the casket retains the heat to permit the heating of the material to a substantially higher temperature than achieveable in the oven without the container.

  14. Container for heat treating materials in microwave ovens

    SciTech Connect

    Holcombe, C.E.; Dykes, N.L.; Kimrey, H.D. Jr.; Mills, J.E.

    1989-03-07

    The efficiency of a microwave oven of a conventional two-source configuration and energy level is increased by providing the oven with a container for housing a refractory material to be treated. The container is formed of top and bottom walls transparent to microwaves while the sidewalls, in a circular configuration, are formed of a nonmetallic material opaque to microwave radiation reflecting the radiation penetrating the top and bottom walls radially inwardly into the center of the container wherein a casket of heat-insulating material is provided for housing the material to be heat treated. The reflection of the microwave radiation from the sidewalls increases the concentration of the microwaves upon the material being heat treated while the casket retains the heat to permit the heating of the material to a substantially higher temperature than achieveable in the oven without the container.

  15. Mineral balance in milk heated using microwave energy.

    PubMed

    de la Fuente, Miguel Angel; Olano, Agustín; Juárez, Manuela

    2002-04-10

    Milk heated to 75 and 85 degrees C in a water bath or in a microwave oven was assayed for changes in salt partitioning after cooling to room temperature. To properly to assess differences and draw valid comparisons, the two heating methods used in the experiment were applied to samples for identical exposure times, and the samples were heated to attain the same final temperatures. Although the soluble Ca and P(i) contents were lower in the heated milk samples, no significant differences in salt partitioning were found between microwave and conventional heating. Ionic calcium levels in the milk samples pasteurized using microwave energy were very close to the levels in the samples heated in a conventional water bath (approximately 90% of the level in the untreated milk samples). The microwave heating-induced changes were completely reversed after storage at 20 degrees C for 24 h. The coagulation properties of the heated milk samples were also examined, and the coagulation time was longer and the curd formation rate slower in the microwave-heated milk than in the raw milk. Still, the experimental results demonstrated that microwave heating was no more detrimental to the milk than conventional heating and could thus be used for pasteurization purposes.

  16. Synthesis of hydroxyapatite nanostructures using microwave heating.

    PubMed

    Cabrera, J L; Velázquez-Castillo, R; Rivera-Muñoz, E M

    2011-06-01

    Hydroxyapatite (HAp) nanoplates and nanofibers have been synthesized using CaNO3, KOH and K2HPO4 as chemical precursors. The concentration of these precursors was kept constant in all experiments. Synthesis reactions were carried out inside of pressurized Teflon vessels. The energy required for the synthesis was supplied by microwaves. Most of the reactions were performed in the presence of glutamic acid. The concentration of this substance was the only difference in the formulation of the reacting mixture, and its effect on the morphology of nanostructures has been evaluated. The use of pressurized vessels and the heating by microwaves in the synthesis reactions made easier the obtaining of HAp crystals. The morphology of nanostructures was influenced through the differences in the concentration of glutamic acid. The variations on the reaction time were useful to obtain nanofibers with an adequate size. The nanoplates and nanofibers obtained will be used to synthesize an organic-inorganic composite which has potential application on medicine and odontology. X-ray diffraction and FTIR were performed to verify the obtaining of a hydroxyapatite phase. High-resolution electron microscopy was carried out for microstructure analyses. Energy-dispersive X-ray spectroscopy was used to evaluate the Ca/P ratio in all nanostructures.

  17. Compact Directional Microwave Antenna for Localized Heating

    NASA Technical Reports Server (NTRS)

    Fink, Patrick W.; Lin, Gregory Y.; Chu, Andrew W.; Dobbins, Justin A.; Arndt, G. Dickey; Ngo, Phong

    2008-01-01

    A directional, catheter-sized cylindrical antenna has been developed for localized delivery of microwave radiation for heating (and thus killing) diseased tissue without excessively heating nearby healthy tissue. By "localized" is meant that the antenna radiates much more in a selected azimuthal direction than in the opposite radial direction, so that it heats tissue much more on one side than it does on the opposite side. This antenna can be inserted using either a catheter or a syringe. A 2.4-mm prototype was tested, although smaller antennas are possible. Prior compact, cylindrical antennas designed for therapeutic localized hyperthermia do not exhibit such directionality; that is, they radiate in approximately axisymmetric patterns. Prior directional antennas designed for the same purpose have been, variously, (1) too large to fit within catheters or (2) too large, after deployment from catheters, to fit within the confines of most human organs. In contrast, the present antenna offers a high degree of directionality and is compact enough to be useable as a catheter in some applications.

  18. New prospects in pretreatment of cotton fabrics using microwave heating.

    PubMed

    Hashem, M; Taleb, M Abou; El-Shall, F N; Haggag, K

    2014-03-15

    As microwaves are known to give fast and rapid volume heating, the present study is undertaken to investigate the use of microwave heating for pretreatment cotton fabrics to reduce the pretreatment time, chemicals and water. The onset of the microwave heating technique on the physicochemical and performance properties of desized, scoured and bleached cotton fabric is elucidated and compared with those obtained on using conventional thermal heating. Combined one-step process for desizing, scouring and bleaching of cotton fabric under microwave heating was also investigated. The dual effect of adding urea, (as microwave absorber and hydrogen peroxide activator) has been exploiting to accelerate the pretreatment reaction of cotton fabric. DSC, FT-IR and SEM have been used to investigate the onset of microwave on the morphological and chemical change of cotton cellulose after pretreatment and bleaching under microwave heating. Results obtained show that, a complete fabric preparation was obtained in just 5 min on using microwave in pretreatments process and the fabric properties were comparable to those obtained in traditional pretreatment process which requires 2.5-3h for completion.

  19. The scientific base of heating water by microwave

    SciTech Connect

    Akdoğan, Ender; Çiftçi, Muharrem

    2016-03-25

    This article is based on the master thesis [4] related to our invention which was published in World Intellectual Property Organization (WO/2011/048506) as a microwave water heater. In the project, a prototype was produced to use microwave in industrial heating. In order to produce the prototype, the most appropriate material kind for microwave-water experiments was determined by a new energy loss rate calculation technique. This new energy loss calculation is a determinative factor for material permeability at microwave frequency band (1-100 GHz). This experimental series aim to investigate the rationality of using microwave in heating industry. Theoretically, heating water by microwave (with steady frequency 2.45 GHz) is analyzed from sub-molecular to Classical Mechanic results of heating. In the study, we examined Quantum Mechanical base of heating water by microwave experiments. As a result, we derived a Semi-Quantum Mechanical equation for microwave-water interactions and thus, Wien displacement law can be derived to verify experimental observations by this equation.

  20. The scientific base of heating water by microwave

    NASA Astrophysics Data System (ADS)

    Akdoǧan, Ender; ćiftçi, Muharrem

    2016-03-01

    This article is based on the master thesis [4] related to our invention which was published in World Intellectual Property Organization (WO/2011/048506) as a microwave water heater. In the project, a prototype was produced to use microwave in industrial heating. In order to produce the prototype, the most appropriate material kind for microwave-water experiments was determined by a new energy loss rate calculation technique. This new energy loss calculation is a determinative factor for material permeability at microwave frequency band (1-100 GHz). This experimental series aim to investigate the rationality of using microwave in heating industry. Theoretically, heating water by microwave (with steady frequency 2.45 GHz) is analyzed from sub-molecular to Classical Mechanic results of heating. In the study, we examined Quantum Mechanical base of heating water by microwave experiments. As a result, we derived a Semi-Quantum Mechanical equation for microwave-water interactions and thus, Wien displacement law can be derived to verify experimental observations by this equation.

  1. Microwave heating for the rapid generation of glycosylhydrazides.

    PubMed

    Mallevre, F; Roget, A; Minon, T; Kervella, Y; Ropartz, D; Ralet, M C; Canut, H; Livache, T

    2013-07-17

    Conditions for simple derivatization of reducing carbohydrates via adipic acid dihydrazide microwave-assisted condensation are described. We demonstrate with a diverse set of oligo- and polysaccharides how to improve a restrictive and labor intensive conventional conjugation protocol by using microwave-assisted chemistry. We show that 5 min of microwave heating in basic or acidic conditions are adequate to generate, in increased yields, intact and functional glycosylhydrazides, whereas hours to days and acidic conditions are generally required under conventional methods.

  2. Heating behavior and crystal growth mechanism in microwave field.

    PubMed

    Yang, Gang; Kong, Yan; Hou, Wenhua; Yan, Qijie

    2005-02-03

    A simple microwave solid-state reactor was designed on the basis of a domestic microwave oven by using graphite powder as heating medium. The heating behavior of the reactor was studied by using an on-line computer to monitor the real-time temperature during irradiation. It was found that the temperature (T) was related to the time (t) and that microwave power depended on the duty cycle (x) of microwave irradiation. Two empirical equations were proposed and could be applied to the similar microwave solid-state reactors. Four inorganic layered materials, LiV(3)O(8), KNb(3)O(8), KTiNbO(5), and KSr(2)Nb(3)O(10), were successfully synthesized in the designed reactor at a suitable heating rate and temperature that were fully controlled by the empirical equations. Characterization results of X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopy, and scanning (SEM) and transmission (TEM) electron microscopy indicated that the phases of samples prepared by traditional and microwave methods were in good agreement; nevertheless, the heating nature and the morphologies of products were quite different. The samples synthesized in the microwave field had crystallographic defects and showed an incompactly stacking structure of nanosheets. Due to the rapid formation of crystallites and different extended growth rate along the crystal axis of the products in microwave field, the crystal growth mechanism of layered metal oxides was not according to that of the traditional method and is briefly discussed.

  3. Multiphysics modeling of microwave heating of whole tomato

    USDA-ARS?s Scientific Manuscript database

    A mathematical model of a food is useful for prediction of temperature profiles during microwave heating. However, due to their complex geometry and interaction with electromagnetic fields, whole tomatoes resist an analytical approach to modeling the fruit as it is subjected to microwave energy. T...

  4. Nonuniformity of Temperatures in Microwave Steam Heating of Lobster Tail.

    PubMed

    Fleischman, Gregory J

    2016-11-01

    The biennial Conference for Food Protection provides a formal process for all interested parties to influence food safety guidance. At a recent conference, an issue was raised culminating in a formal request to the U.S. Food and Drug Administration to change its Food Code recommendation for safe cooking of seafood using microwave energy when steaming was also employed. The request was to treat microwave steam cooked seafood as a conventionally cooked raw animal product rather than a microwave cooked product, for which the safe cooking recommendation is more extensive owing to the complex temperature distributions in microwave heating. The request was motivated by a literature study that revealed a more uniform temperature distribution in microwave steam cooked whole lobster. In that study, single-point temperatures were recorded in various sections of the whole lobster, but only one temperature was recorded in the tail, although the large size of the tail could translate to multiple hot and cold points. The present study was conducted to examine lobster tail specifically, measuring temperatures at multiple points during microwave steam cooking. Large temperature differences, greater than 60°C at times, were found throughout the heating period. To compensate for such differences, the Food Code recommends a more extensive level of cooking when microwave energy, rather than conventional heat sources, is used. Therefore, a change in the Food Code regarding microwave steam heating cannot be recommended.

  5. Flow-Dependent Vascular Heat Transfer during Microwave Thermal Ablation

    PubMed Central

    Chiang, Jason; Hynes, Kieran; Brace, Christopher L.

    2012-01-01

    Microwave tumor ablation is an attractive option for thermal ablation because of its inherent benefits over radiofrequency ablation (RFA) in the treatment of solid tumors such as hepatocellular carcinoma (HCC). Microwave energy heats tissue to higher temperatures and at a faster rate than RFA, creating larger, more homogenous ablation zones. In this study, we investigate microwave heating near large vasculature using coupled fluid-flow and thermal analysis. Low-flow conditions are predicted to be more likely to cause cytotoxic heating and, therefore, vessel thrombosis and endothelial damage of downstream tissues. Such conditions may be more prevalent in patient with severe cirrhosis or compromised blood flow. High-flow conditions create the more familiar heat-sink effect that can protect perivascular tissues from the intended thermal damage. These results may help guide placement and use of microwave ablation technologies in future studies. PMID:23367194

  6. Flow-dependent vascular heat transfer during microwave thermal ablation.

    PubMed

    Chiang, Jason; Hynes, Kieran; Brace, Christopher L

    2012-01-01

    Microwave tumor ablation is an attractive option for thermal ablation because of its inherent benefits over radiofrequency ablation (RFA) in the treatment of solid tumors such as hepatocellular carcinoma (HCC). Microwave energy heats tissue to higher temperatures and at a faster rate than RFA, creating larger, more homogenous ablation zones. In this study, we investigate microwave heating near large vasculature using coupled fluid-flow and thermal analysis. Low-flow conditions are predicted to be more likely to cause cytotoxic heating and, therefore, vessel thrombosis and endothelial damage of downstream tissues. Such conditions may be more prevalent in patient with severe cirrhosis or compromised blood flow. High-flow conditions create the more familiar heat-sink effect that can protect perivascular tissues from the intended thermal damage. These results may help guide placement and use of microwave ablation technologies in future studies.

  7. Synthesis and Modification of Carbon Nanomaterials utilizing Microwave Heating.

    PubMed

    Schwenke, Almut M; Hoeppener, Stephanie; Schubert, Ulrich S

    2015-07-22

    Microwave-assisted synthesis and processing represents a growing field in materials research and successfully entered the field of carbon nanomaterials during the last decade. Due to the strong interaction of carbon materials with microwave radiation, fast heating rates and localized heating can be achieved. These features enable the acceleration of reaction processes, as well as the formation of nanostructures with special morphologies. A comprehensive overview is provided here on the possibilities and achievements in the field of carbon-nanomaterial research when using microwave-based heating approaches. This includes the synthesis and processing of carbon nanotubes and fibers, graphene materials, carbon nanoparticles, and capsules, as well as porous carbon materials. Additionally, the principles of microwave-heating, in particular of carbon materials, are introduced and important issues, i.e., safety and reproducibility, are discussed.

  8. Microwave heating and the acceleration of polymerization processes

    NASA Astrophysics Data System (ADS)

    Parodi, Fabrizio

    1999-12-01

    Microwave power irradiation of dielectrics is nowadays well recognized and extensively used as an exceptionally efficient and versatile heating technique. Besides this, it revealed since the early 1980s an unexpected, and still far from being elucidated, capacity of causing reaction and yield enhancements in a great variety of chemical processes. These phenomena are currently referred to as specific or nonthermal effects of microwaves. An overview of them and their interpretations given to date in achievements in the microwave processing of slow-curing thermosetting resins is also given. Tailored, quaternary cyanoalkoxyalkyl ammonium halide catalysts, further emphasizing the microwave enhancements of curing kinetics of isocyanate/epoxy and epoxy/anhydride resin systems, are here presented. Their catalytic efficiency under microwave irradiation, microwave heatability, and dielectric properties are discussed and interpreted by the aid of the result of semi-empirical quantum mechanics calculations and molecule dynamics simulations in vacuo. An ion-hopping conduction mechanism has been recognized as the dominant source of the microwave absorption capacities of these catalysts. Dipolar relaxation losses by their strongly dipolar cations, viceversa, would preferably be responsible for the peculiar catalytic effects displayed under microwave heating. This would occur through a well-focused, molecular microwave overheating of intermediate reactive anionic groupings, they could indirectly cause as the nearest neighbors of such negatively-charged molecular sites.

  9. Container for heat treating materials in microwave ovens

    SciTech Connect

    Holcombe, C.E.; Dykes, N.L.; Kimrey, H.D. Jr.; Mills, J.E.

    1989-03-07

    This patent describes a container for heating refractory material in a microwave oven to receive microwave radiation from microwave radiation emitting means disposed on at least one of vertically separated sides of a volume in the oven. The container positionable within and essentially filling the vertical expanse of the volume and comprising top wall means and bottom wall means each formed of a material substantially transparent to and non-coupling with microwave radiation, vertical wall means disposed between and contacting the top wall means and the bottom wall means for defining therewith an enclosed chamber. The vertical wall means being formed of graphite or a graphite composite characterized by being substantially opaque to and non-coupling with microwave radiation for reflecting microwave radiation inwardly into the chamber.

  10. New automated microwave heating process for cooking and pasteurization of microwaveable foods containing raw meats.

    PubMed

    Huang, Lihan; Sites, Joseph

    2010-03-01

    A new microwave heating process was developed for cooking microwaveable foods containing raw meats. A commercially available inverter-based microwave oven was modified for pasteurization of mechanically tenderized beef, inoculated with Escherichia coli O157:H7 (approximately 5 log(10) CFU/g) and packaged in a 12-oz CPET tray containing 150-mL de-ionized water. The new microwave heating system was equipped with an infrared sensor and a proportional feedback mechanism to allow temperature controlled microwave heating. A 2-stage heating strategy was adopted to cook the product. In the primary heating stage, the sample surface temperature was increased to an initial temperature set-point (ITSP, 65, 70, 75, or 80 degrees C). In the secondary heating stage, the heating was continued with a small fraction of microwave power. The effect of ITSP, hold time (0 to 3 min), and sample elevation (0, 0.03, and 0.07 m above turntable) on inactivation of E. coli O157:H7 and background microflora was evaluated. It was observed that only a small number (approximately 1.3 logs) of E. coli O157:H7 and background microflora were inactivated in the primary heating stage. The elevation 0.07 m, which was in the proximity of the geometric center of the metal cavity, was more effective in inactivating both E. coli O157:H7 and background microflora. Substantially more bacteria were inactivated in the secondary heating stage. Complete inactivation of E. coli and background microflora was observed with heating at temperatures above 70 degrees C for more than 1 min. This study demonstrated a new approach for ensuring the safety of microwaveable products containing raw meats.

  11. Elimination of Salmonella in Microwaveable Non-Ready-to-Eat Meats by Power-Controlled Microwave Heating

    USDA-ARS?s Scientific Manuscript database

    Microwaveable non-ready-to-eat (NRTE) foods belong to a category of products that contain raw ingredients (such as chicken meats). These products are usually frozen and heated in a microwave oven prior to consumption. As the products are not uniformly cooked during microwave heating, human pathoge...

  12. Assessment of heating rate and non-uniform heating in domestic microwave ovens.

    PubMed

    Pitchai, Krishnamoorthy; Birla, Sohan L; Jones, David; Subbiah, Jeyamkondan

    2012-01-01

    Due to the inherent nature of standing wave patterns of microwaves inside a domestic microwave oven cavity and varying dielectric properties of different food components, microwave heating produces non-uniform distribution of energy inside the food. Non-uniform heating is a major food safety concern in not-ready-to-eat (NRTE) microwaveable foods. In this study, we present a method for assessing heating rate and non-uniform heating in domestic microwave ovens. In this study a custom designed container was used to assess heating rate and non-uniform heating of a range of microwave ovens using a hedgehog of 30 T-type thermocouples. The mean and standard deviation of heating rate along the radial distance and sector of the container were measured and analyzed. The effect of the location of rings and sectors was analyzed using ANOVA to identify the best location for placing food on the turntable. The study suggested that the best location to place food in a microwave oven is not at the center but near the edge of the turntable assuming uniform heating is desired. The effect of rated power and cavity size on heating rate and non-uniform heating was also studied for a range of microwave ovens. As the rated power and cavity size increases, heating rate increases while non-uniform heating decreases. Sectors in the container also influenced heating rate (p < 0.0001), even though it did not have clear trend on heating rate. In general, sectors close to the magnetron tend to heat slightly faster than sectors away from the magnetron. However, the variation in heating rate among sectors was only 2 degrees C/min and considered not practically important. Overall heating performance such as mean heating rate and non-uniform heating did not significantly vary between the two replications that were performed 4 h apart. However, microwave ovens were inconsistent in producing the same heating patterns between the two replications that were performed 4 h apart.

  13. Cardiac tissue ablation with catheter-based microwave heating.

    PubMed

    Rappaport, C

    2004-11-01

    The common condition of atrial fibrillation is often treated by cutting diseased cardiac tissue to disrupt abnormal electrical conduction pathways. Heating abnormal tissue with electromagnetic power provides a minimally invasive surgical alternative to treat these cardiac arrhythmias. Radio frequency ablation has become the method of choice of many physicians. Recently, microwave power has also been shown to have great therapeutic benefit in medical treatment requiring precise heating of biological tissue. Since microwave power tends to be deposited throughout the volume of biological media, microwave heating offers advantages over other heating modalities that tend to heat primarily the contacting surface. It is also possible to heat a deeper volume of tissue with more precise control using microwaves than with purely thermal conduction or RF electrode heating. Microwave Cardiac Ablation (MCA) is used to treat heart tissue that allows abnormal electrical conduction by heating it to the point of inactivation. Microwave antennas that fit within catheter systems can be positioned close to diseased tissue. Specialized antenna designs that unfurl from the catheter within the heart can then radiate specifically shaped fields, which overcome problems such as excessive surface heating at the contact point. The state of the art in MCA is reviewed in this paper and a novel catheter-based unfurling wide aperture antenna is described. This antenna consists of the centre conductor of a coaxial line, shaped into a spiral and insulated from blood and tissue by a non-conductive fluid filled balloon. Initially stretched straight inside a catheter for transluminal guiding, once in place at the cardiac target, the coiled spiral antenna is advanced into the inflated balloon. Power is applied in the range of 50-150 W at the reserved industrial, scientific and medical (ISM) frequency of 915 MHz for 30-90 s to create an irreversible lesion. The antenna is then retracted back into the

  14. Containerless synthesis of ceramic materials using microwave heating

    NASA Technical Reports Server (NTRS)

    Dunn, B.; Crouch-Baker, S.

    1990-01-01

    It was demonstrated that microwave heating technique may be employed for the synthesis of a number of multicomponent ceramic oxide-based materials, e.g., YBa2Cu3O7 and CuFe2O4. A characteristic, and potentially extremely useful, feature of such synthesis is that they occur in significantly less time than that required using conventional furnace-based techniques. However, the information obtained to date is necessarily rather empirical, and systematic investigations of the use of microwave heating for the synthesis of ceramic materials are required. The synthesis of ceramic materials at high temperatures are often affected by unwanted, deleterious reactions of the reactants and/or products with the reaction container. Consequently, it is of interest to investigate the high temperature synthesis of ceramic materials using microwave heating in a containerless environment.

  15. [Study on catalytic oxidation of benzene by microwave heating].

    PubMed

    Zhang, Yu-cai; Bo, Long-li; Wang, Xiao-hui; Liu, Hai-nan; Zhang, Hao

    2012-08-01

    The performance in catalytic oxidation of benzene was investigated in two different heating modes, microwave heating and conventional electric furnace heating. The effects of copper (Cu)-manganese (Mn) mass ratio, doping dose of cerium (Ce) and calcination temperature on the catalytic activity of Cu-Mn-Ce/molecular sieve catalyst were also checked in catalytic oxidation of benzene with microwave heating, and the catalysts were subsequently characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that the catalyst had better catalytic activity for the oxidation of benzene under microwave heating than electric furnace heating, and high oxidation efficiency for benzene was reached due to the "local hot spots" and dipole polarization effect of microwave and stable bed reaction temperature. Under the conditions of Cu, Mn and Ce mass ratio 1:1:0.33 and calcination temperature 500 degrees C, the catalyst had the optimal catalytic activity for benzene oxidation, and its light-off temperature and complete combustion temperature were 165 degrees C and 230 degrees C, respectively. It was indicated by characteristics of XRD and SEM that the presence of copper and manganese oxides and Cu1.5Mn1.5O4 with spinel crystal improved the catalytic activity of the catalyst, and the doping of Ce promoted the dispersion and regularization of active components. High calcination temperature led to the sintering of the catalyst surface and agglomeration of active components, which decreased the catalytic activity of the catalyst in the catalytic oxidation

  16. Synthesis of ultrafine powders by microwave heating

    DOEpatents

    Meek, T.T.; Sheinberg, H.; Blake, R.D.

    1987-04-24

    A method of synthesizing ultrafine powders using microwaves is described. A water soluble material is dissolved in water and the resulting aqueous solution is exposed to microwaves until the water has dissolved. The resulting material is an ultrafine powder. This method can be used to make Al/sub 2/O/sub 3/, NiO /plus/ Al/sub 2/O/sub 3/ and NiO as well as a number of other materials including GaBa/sub 2/Cu/sub 3/O/sub x/. 1 tab.

  17. Synthesis of ultrafine powders by microwave heating

    DOEpatents

    Meek, Thomas T.; Sheinberg, Haskell; Blake, Rodger D.

    1988-01-01

    A method of synthesizing ultrafine powders using microwaves is described. A water soluble material is dissolved in water and the resulting aqueous solution is exposed to microwaves until the water has been removed. The resulting material is an ultrafine powder. This method can be used to make Al.sub.2 O.sub.3, NiO+Al.sub.2 O.sub.3 and NiO as well as a number of other materials including GaBa.sub.2 Cu.sub.3 O.sub.x.

  18. Beneficial effects of microwave-assisted heating versus conventional heating in noble metal nanoparticle synthesis.

    PubMed

    Dahal, Naween; García, Stephany; Zhou, Jiping; Humphrey, Simon M

    2012-11-27

    An extensive comparative study of the effects of microwave versus conventional heating on the nucleation and growth of near-monodisperse Rh, Pd, and Pt nanoparticles has revealed distinct and preferential effects of the microwave heating method. A one-pot synthetic method has been investigated, which combines nucleation and growth in a single reaction via precise control over the precursor addition rate. Using this method, microwave-assisted heating enables the convenient preparation of polymer-capped nanoparticles with improved monodispersity, morphological control, and higher crystallinity, compared with samples heated conventionally under otherwise identical conditions. Extensive studies of Rh nanoparticle formation reveal fundamental differences during the nucleation phase that is directly dependent on the heating method; microwave irradiation was found to provide more uniform seeds for the subsequent growth of larger nanostructures of desired size and surface structure. Nanoparticle growth kinetics are also markedly different under microwave heating. While conventional heating generally yields particles with mixed morphologies, microwave synthesis consistently provides a majority of tetrahedral particles at intermediate sizes (5-7 nm) or larger cubes (8+ nm) upon further growth. High-resolution transmission electron microscopy indicates that Rh seeds and larger nanoparticles obtained from microwave-assisted synthesis are more highly crystalline and faceted versus their conventionally prepared counterparts. Microwave-prepared Rh nanoparticles also show approximately twice the catalytic activity of similar-sized conventionally prepared particles, as demonstrated in the vapor-phase hydrogenation of cyclohexene. Ligand exchange reactions to replace polymer capping agents with molecular stabilizing agents are also easily facilitated under microwave heating, due to the excitation of polar organic moieties; the ligand exchange proceeds with excellent retention of

  19. Directional melting of alumina via polarized microwave heating

    NASA Astrophysics Data System (ADS)

    Hu, Yuan; Nakano, Aiichiro; Wang, Joseph

    2017-01-01

    Dynamical instabilities and melting of crystals upon heating are fundamental problems in physics and materials science. Using molecular dynamics simulations, we found that drastically different melting temperatures and behaviors can be achieved in α-alumina using microwave heating, where the electric field is aligned with different crystallographic orientations. Namely, alumina melts much earlier at lower temperatures when the electric field is parallel to the c-axis. The atomistic mechanism was identified as selective liberation of the Al sublattice due to the shear instability along the c-axis. This directional melting concept may be used for triggering distinct dynamical instabilities and melting of dielectric crystals using polarized microwave fields.

  20. Numerical Analysis of Microwave Heating on Saponification Reaction

    NASA Astrophysics Data System (ADS)

    Huang, Kama; Jia, Kun

    2005-01-01

    Currently, microwave is widely used in chemical industry to accelerate chemical reactions. Saponification reaction has important applications in industry; some research results have shown that microwave heating can significantly accelerate the reaction [1]. But so far, no efficient method has been reported for the analysis of the heating process and design of an efficient reactor powered by microwave. In this paper, we present a method to study the microwave heating process on saponification reaction, where the reactant in a test tube is considered as a mixture of dilute solution. According to the preliminary measurement results, the effective permittivity of the mixture is approximately the permittivity of water, but the conductivity, which could change with the reaction, is derived from the reaction equation (RE). The electromagnetic field equation and reaction equation are coupled by the conductivity. Following that, the whole heating processes, which is described by Maxwell's equations, the reaction equation and heat transport equation (HTE), is analyzed by finite difference time domain (FDTD) method. The temperature rising in the test tube are measured and compared with the computational results. Good agreement can be seen between the measured and calculated results.

  1. Microwave Dielectric Heating of Drops in Microfluidic Devices†

    PubMed Central

    Issadore, David; Humphry, Katherine J.; Brown, Keith A.; Sandberg, Lori; Weitz, David; Westervelt, Robert M.

    2010-01-01

    We present a technique to locally and rapidly heat water drops in microfluidic devices with microwave dielectric heating. Water absorbs microwave power more efficiently than polymers, glass, and oils due to its permanent molecular dipole moment that has a large dielectric loss at GHz frequencies. The relevant heat capacity of the system is a single thermally isolated picoliter drop of water and this enables very fast thermal cycling. We demonstrate microwave dielectric heating in a microfluidic device that integrates a flow-focusing drop maker, drop splitters, and metal electrodes to locally deliver microwave power from an inexpensive, commercially available 3.0 GHz source and amplifier. The temperature of the drops is measured by observing the temperature dependent fluorescence intensity of cadmium selenide nanocrystals suspended in the water drops. We demonstrate characteristic heating times as short as 15 ms to steady-state temperatures as large as 30°C above the base temperature of the microfluidic device. Many common biological and chemical applications require rapid and local control of temperature, such as PCR amplification of DNA, and can benefit from this new technique. PMID:19495453

  2. Microwave dielectric heating of drops in microfluidic devices.

    PubMed

    Issadore, David; Humphry, Katherine J; Brown, Keith A; Sandberg, Lori; Weitz, David A; Westervelt, Robert M

    2009-06-21

    We present a technique to locally and rapidly heat water drops in microfluidic devices with microwave dielectric heating. Water absorbs microwave power more efficiently than polymers, glass, and oils due to its permanent molecular dipole moment that has large dielectric loss at GHz frequencies. The relevant heat capacity of the system is a single thermally isolated picolitre-scale drop of water, enabling very fast thermal cycling. We demonstrate microwave dielectric heating in a microfluidic device that integrates a flow-focusing drop maker, drop splitters, and metal electrodes to locally deliver microwave power from an inexpensive, commercially available 3.0 GHz source and amplifier. The temperature change of the drops is measured by observing the temperature dependent fluorescence intensity of cadmium selenide nanocrystals suspended in the water drops. We demonstrate characteristic heating times as short as 15 ms to steady-state temperature changes as large as 30 degrees C above the base temperature of the microfluidic device. Many common biological and chemical applications require rapid and local control of temperature and can benefit from this new technique.

  3. Spatial observation and quantification of microwave heating in materials

    NASA Astrophysics Data System (ADS)

    Crane, C. A.; Pantoya, M. L.; Weeks, B. L.

    2013-08-01

    An electromagnetic exposure chamber was designed to safely deliver electromagnetic power in the range of microwaves between 0.8 and 4.2 GHz to a thin cylindrical materials. This instrumentation is unique because the diagnostics not only measure sample heating with a response time of 1.3 ms, but also energy transmitted and reflected. Energy absorption at different frequencies was quantified via electromagnetic heating using an infrared camera. This in situ IR imaging of the spatial distribution of temperature during microwave exposure coupled with sensors for determining transmitted and reflected energy enables novel new microwave energy experiments. Samples were exposed to a portion of both the electric and magnetic fields inside a waveguide and based on sample dimensions, the field strengths were assumed uniform across the sample. Three materials were examined: two were borosilicate, first coated with graphite paint and a second without the coating; and, the third was a compressed sample of flake graphite pressed to 69% of its bulk density. Results are in agreement with the theories of microwave heating and verify the functionality of this experimental design. This diagnostic will be important in future tests where a variety of different materials can be exposed to weak electromagnetic waves and their efficiency in coupling to the microwaves can be examined.

  4. Rapid Nanoparticle Synthesis by Magnetic and Microwave Heating.

    PubMed

    Chikan, Viktor; McLaurin, Emily J

    2016-05-05

    Traditional hot-injection (HI) syntheses of colloidal nanoparticles (NPs) allows good separation of the nucleation and growth stages of the reaction, a key limitation in obtaining monodisperse NPs, but with limited scalability. Here, two methods are presented for obtaining NPs via rapid heating: magnetic and microwave-assisted. Both of these techniques provide improved engineering control over the separation of nucleation and growth stages of nanomaterial synthesis when the reaction is initiated from room temperature. The advantages of these techniques with preliminary data are presented in this prospective article. It is shown here that microwave assisted heating could possibly provide some selectivity in activating the nanomaterial precursor materials, while magnetic heating can produce very tiny particles in a very short time (even on the millisecond timescale), which is important for scalability. The fast magnetic heating also allows for synthesizing larger particles with improved size distribution, therefore impacting, not only the quantity, but the quality of the nanomaterials.

  5. Rapid Nanoparticle Synthesis by Magnetic and Microwave Heating

    PubMed Central

    Chikan, Viktor; McLaurin, Emily J.

    2016-01-01

    Traditional hot-injection (HI) syntheses of colloidal nanoparticles (NPs) allows good separation of the nucleation and growth stages of the reaction, a key limitation in obtaining monodisperse NPs, but with limited scalability. Here, two methods are presented for obtaining NPs via rapid heating: magnetic and microwave-assisted. Both of these techniques provide improved engineering control over the separation of nucleation and growth stages of nanomaterial synthesis when the reaction is initiated from room temperature. The advantages of these techniques with preliminary data are presented in this prospective article. It is shown here that microwave assisted heating could possibly provide some selectivity in activating the nanomaterial precursor materials, while magnetic heating can produce very tiny particles in a very short time (even on the millisecond timescale), which is important for scalability. The fast magnetic heating also allows for synthesizing larger particles with improved size distribution, therefore impacting, not only the quantity, but the quality of the nanomaterials. PMID:28335212

  6. Apparatus with moderating material for microwave heat treatment of manufactured components

    SciTech Connect

    Ripley, Edward B

    2011-05-10

    An apparatus for heat treating manufactured components using microwave energy and microwave susceptor material. Heat treating medium such as eutectic salts may be employed. A fluidized bed introduces process gases which may include carburizing or nitriding gases The process may be operated in a batch mode or continuous process mode. A microwave heating probe may be used to restart a frozen eutectic salt bath.

  7. Effects of polarization-charge shielding in microwave heating

    SciTech Connect

    Lin, M. S.; Lin, S. M.; Chiang, W. Y.; Barnett, L. R.; Chu, K. R.

    2015-08-15

    Heating of dielectric objects by radio frequency (RF) and microwaves has long been a method widely employed in scientific research and industrial applications. However, RF and microwave heating are often susceptible to an excessive temperature spread due to uneven energy deposition. The current study elucidates an important physical reason for this difficulty and proposes an effective remedy. Non-spherical samples are placed in an anechoic chamber, where it is irradiated by a traveling microwave wave with 99% intensity uniformity. Polarization charges induced on the samples tend to partially cancel the incident electric field and hence reduce the heating rate. The polarization-charge shielded heating rate is shown to be highly dependent on the sample's shape and its orientation relative to the wave electric field. For samples with a relatively high permittivity, the resultant uneven heating can become a major cause for the excessive temperature spread. It is also demonstrated that a circularly polarized wave, with its rapidly rotating electric field, can effectively even out the heating rate and hence the temperature spread.

  8. The influence of microwave heating on the characteristics of polyelectrolytes.

    PubMed

    Martin, D; Mateescu, E; Ighigeanu, D; Jianu, A

    2000-01-01

    Results obtained by microwave (MW) and simultaneous microwave and electron beam (MW + EB) application in the chemistry of acrylamide and acrylic acid co-polymers (PA type polyelectrolytes) are presented. Comparative results concerning the molecular weight (Mw) and Huggins' constant for the acrylamide copolymers obtained by classical heating, MW heating, EB irradiation and simultaneous MW + EB treatment are reported. MW heating produces high PA water solubility but median Mw values; EB irradiation gives high Mw values but associated with a cross-linked structure (poor water solubility) while MW energy addition to EB energy gives simultaneously high Mw values and high PA water solubility. A MW installation of 2.45 GHz and 2.5 kW, designed to provide small-scale commercial production of PA polyelectrolytes, is described.

  9. Ceramic-glass-metal seal by microwave heating

    DOEpatents

    Meek, T.T.; Blake, R.D.

    1983-10-04

    A method for producing a ceramic-glass-metal seal by microwaving, mixes a slurry of glass sealing material and coupling agent and applies same to ceramic and metal workpieces. The slurry and workpieces are then insulated and microwaved at a power, time and frequency sufficient to cause a liquid-phase reaction in the slurry. The reaction of the glass sealing material forms a chemically different seal than that which would be formed by conventional heating because it is formed by diffusion rather than by wetting of the reactants.

  10. Ceramic-glass-ceramic seal by microwave heating

    DOEpatents

    Meek, T.T.; Blake, R.D.

    1983-10-04

    A method for producing a ceramic-glass-ceramic seal by microwaving, mixes a slurry of glass sealing material and coupling agent and applies same to ceramic workpieces. The slurry and workpieces are placed together, insulated and then microwaved at a power, time and frequency sufficient to cause a liquid phase reaction in the slurry. The reaction of the glass sealing material forms a chemically different seal than that which would be formed by conventional heating because it is formed by a diffusion rather than by wetting of the reactants.

  11. Ceramic-glass-ceramic seal by microwave heating

    DOEpatents

    Meek, Thomas T.; Blake, Rodger D.

    1985-01-01

    A method for producing a ceramic-glass-ceramic seal by microwaving, mixes a slurry of glass sealing material and coupling agent and applies same to ceramic workpieces. The slurry and workpieces are placed together, insulated and then microwaved at a power, time and frequency sufficient to cause a liquid phase reaction in the slurry. The reaction of the glass sealing material forms a chemically different seal than that which would be formed by conventional heating because it is formed by a diffusion rather than by wetting of the reactants.

  12. Ceramic-glass-metal seal by microwave heating

    DOEpatents

    Meek, Thomas T.; Blake, Rodger D.

    1985-01-01

    A method for producing a ceramic-glass-metal seal by microwaving mixes a slurry of glass sealing material and coupling agent and applies same to ceramic and metal workpieces. The slurry and workpieces are then insulated and microwaved at a power, time and frequency sufficient to cause a liquid phase reaction in the slurry. The reaction of the glass sealing material forms a chemically different seal than that which would be formed by conventional heating because it is formed by diffusion rather than by wetting of the reactants.

  13. Microwave Absorption Characteristics of Conventionally Heated Nonstoichiometric Ferrous Oxide

    NASA Astrophysics Data System (ADS)

    Peng, Zhiwei; Hwang, Jiann-Yang; Mouris, Joe; Hutcheon, Ron; Sun, Xiang

    2011-08-01

    The temperature dependence of the microwave absorption of conventionally heated nonstoichiometric ferrous oxide (Fe0.925O) was characterized via the cavity perturbation technique between 294 K and 1373 K (21 °C and 1100 °C). The complex relative permittivity and permeability of the heated Fe0.925O sample slightly change with temperature from 294 K to 473 K (21 °C to 200 °C). The dramatic variations of permittivity and permeability of the sample from 473 K to 823 K (200 °C to 550 °C) are partially attributed to the formation of magnetite (Fe3O4) and metal iron (Fe) from the thermal decomposition of Fe0.925O, as confirmed by the high-temperature X-ray diffraction (HT-XRD). At higher temperatures up to 1373 K (1100 °C), it is found that Fe0.925O regenerates and remains as a stable phase with high permittivity. Since the permittivity dominates the microwave absorption of Fe0.925O above 823 K (550 °C), resulting in shallow microwave penetration depth (~0.11 and ~0.015 m at 915 and 2450 MHz, respectively), the regenerated nonstoichiometric ferrous oxide exhibits useful microwave absorption capability in the temperature range of 823 K to1373 K (550 °C to 1100 °C).

  14. Microwave thermal imaging of scanned focused ultrasound heating: Phantom results

    PubMed Central

    Meaney, Paul M.; Zhou, Tian; Fanning, Margaret W.; Geimer, Shireen D.; Paulsen, Keith D.

    2009-01-01

    We are developing a microwave tomographic imaging system capable of monitoring thermal distributions based on the temperature dependence of the recovered dielectric properties. The system has been coupled to a high intensity focused ultrasound (HIFU) therapy device which can be mechanically steered under computer control to generate arbitrarily shaped heating zones. Their integration takes advantage of the focusing capability of ultrasound for the therapy delivery and the isolation of the microwave imaging signal from the power deposition source to allow simultaneous treatment monitoring. We present several sets of phantom experiments involving different types of heating patterns that demonstrate the quality of both the spatial and temporal thermal imaging performance. This combined approach is adaptable to multiple anatomical sites and may have the potential to be developed into a viable alternative to current clinical temperature monitoring devices for HIFU, such magnetic resonance (MR) imaging. PMID:18608588

  15. Microwave dielectric heating-mediated modification of polymers

    SciTech Connect

    Yalpani, M.

    1995-12-01

    Microwave dielectric heating (MDH) has recently been explored for various inorganic and organic reactions. Reaction rate enhancements of up to three orders of magnitude and altered selectivities have been reported as potential advantages over traditional heating techniques. For synthetic polymers, MDH techniques have been applied to synthesis and processing, and for biopolymers, their uses for starch solubilization, cellulose hydrolysis and non-degradative DNA denaturation have been described. This paper will report on MDH-mediated modifications of several water soluble polymers on a multigram scale, using open reaction vessels in a commercial microwave oven. MDH modifications, such as amidations, etherifications and esterifications, were performed in different reaction media over periods of 1-10 minutes. Compared to conventional reaction techniques, the MDH-mediated modifications proceeded with high conversion efficiencies in substantially shorter reaction times. Examples of modifications of cyclodextrins, cellulose derivatives, as well as polyvinyl alcohol will be discussed.

  16. Microwave thermal imaging of scanned focused ultrasound heating: phantom results.

    PubMed

    Meaney, Paul M; Zhou, Tian; Fanning, Margaret W; Geimer, Shireen D; Paulsen, Keith D

    2008-11-01

    We are developing a microwave tomographic imaging system capable of monitoring thermal distributions based on the temperature dependence of the recovered dielectric properties. The system has been coupled to a high intensity focused ultrasound (HIFU) therapy device which can be mechanically steered under computer control to generate arbitrarily shaped heating zones. Their integration takes advantage of the focusing capability of ultrasound for the therapy delivery and the isolation of the microwave imaging signal from the power deposition source to allow simultaneous treatment monitoring. We present several sets of phantom experiments involving different types of heating patterns that demonstrate the quality of both the spatial and temporal thermal imaging performance. This combined approach is adaptable to multiple anatomical sites and may have the potential to be developed into a viable alternative to current clinical temperature monitoring devices for HIFU, such magnetic resonance (MR) imaging.

  17. Structural characteristics of pumpkin pectin extracted by microwave heating.

    PubMed

    Yoo, Sang-Ho; Lee, Byeong-Hoo; Lee, Heungsook; Lee, Suyong; Bae, In Young; Lee, Hyeon Gyu; Fishman, Marshall L; Chau, Hoa K; Savary, Brett J; Hotchkiss, Arland T

    2012-11-01

    To improve extraction yield of pumpkin pectin, microwave heating was adopted in this study. Using hot acid extraction, pumpkin pectin yield decreased from 5.7% to 1.0% as pH increased from pH 1.0 to 2.0. At pH 2.5, no pectin was recovered from pumpkin flesh powder. After a pretreatment at pH 1.0 and 25 °C for 1 h, pumpkin powder was microwave-extracted at 120 °C for 3 min resulting in 10.5% of pectin yield. However, premicrowave treatment at 60 °C for 20 min did not improve extraction yield. When microwave heating at 80 °C for 10 min was applied after premicrowave treatment, final pectin yield increased to 11.3%. When pH was adjusted to 2.0, the yield dropped to 7.7% under the same extraction conditions. Molecular shape and properties as well as chemical composition of pumpkin pectin were significantly affected depending on extraction methods. Galacturonic acid content (51% to 58%) of pumpkin pectin was lower than that detected in commercial acid-extracted citrus pectin, while higher content of neutral sugars and acetyl esters existed in pumpkin pectin structure. Molecular weight (M(w) ) and intrinsic viscosity (η(w) ) determined for microwave-extracted pumpkin pectins were substantially lower than acid-extracted pectin, whereas polydispersity was greater. However, microwave-extracted pectin at pH 2.0 had more than 5 times greater M(w) than did the pectin extracted at pH 1.0. The η(w) of microwave-extracted pectin produced at pH 2.0 was almost twice that of other microwave-extracted pectins, which were comparable to that of acid-extracted pectin. These results indicate that extraction yield of pumpkin pectin would be improved by microwave extraction and different pectin structure and properties can be obtained compared to acid extraction. Pumpkin is a promising alternative source for pectin material. Pumpkin pectin has a unique chemical structure and physical properties, presumably providing different functional properties compared to conventional commercial

  18. Structural characteristics of pumpkin pectin extracted by microwave heating

    USDA-ARS?s Scientific Manuscript database

    To improve extraction yield of pumpkin pectin, microwave heating was adopted in this study. Using traditional hot acid extraction, pumpkin pectin yield decreased from 5.7 to 1.0 % as pH increased from pH 1.0 to 2.0. At pH 2.5, no pectin was recovered from pumpkin flesh powder. After a pre-treatment ...

  19. Modeling of well drilling heating on crude oil using microwave

    NASA Astrophysics Data System (ADS)

    Muntini, Melania Suweni; Pramono, Yono Hadi; Yustiana

    2016-03-01

    As the world's oil reserves are dwindling, some researchers have been prompted to make a breakthrough to further improve the efficiency of exploration and production. One of the technologies used is heating the crude oil. This paper presents the modeling results of heat treatment on crude oil using microwave energy. Modeling is conducted by assuming that the diameter of the well is 11,16 cm, the heat source is applied on the surface of the well, and the cut-off frequency in the air and on crude oil are 1,56 GHz. and 0.91 GHz, respectively. The energy generated by the microwave radiation is converted into heat energy which is absorbed by the crude oil. Consequently, this energy increases the temperature of crude oil through a heat transfer mechanism. The results obtained showed that the temperature of crude oil is about 200°C at a depth of 62.5cm, and at a distance of 3 cm from the center of the well. Temperature along the well follows an exponential function, which is from the center of the well in the direction radially outward from the cylinder axis. It has been observed that the temperature decreases as measured from the well surface along the cylinder.

  20. Modeling of well drilling heating on crude oil using microwave

    SciTech Connect

    Muntini, Melania Suweni Pramono, Yono Hadi; Yustiana

    2016-03-11

    As the world’s oil reserves are dwindling, some researchers have been prompted to make a breakthrough to further improve the efficiency of exploration and production. One of the technologies used is heating the crude oil. This paper presents the modeling results of heat treatment on crude oil using microwave energy. Modeling is conducted by assuming that the diameter of the well is 11,16 cm, the heat source is applied on the surface of the well, and the cut-off frequency in the air and on crude oil are 1,56 GHz. and 0.91 GHz, respectively. The energy generated by the microwave radiation is converted into heat energy which is absorbed by the crude oil. Consequently, this energy increases the temperature of crude oil through a heat transfer mechanism. The results obtained showed that the temperature of crude oil is about 200°C at a depth of 62.5cm, and at a distance of 3 cm from the center of the well. Temperature along the well follows an exponential function, which is from the center of the well in the direction radially outward from the cylinder axis. It has been observed that the temperature decreases as measured from the well surface along the cylinder.

  1. Viability and antigenicity of anisakis simplex after conventional and microwave heating at fixed temperatures.

    PubMed

    Vidaček, Sanja; De Las Heras, Cristina; Solas, Maria Teresa; García, Maria Luisa; Mendizábal, Angel; Tejada, Margarita

    2011-12-01

    Inactivation of parasites in food by microwave treatment may vary due to differences in the characteristics of microwave ovens and food properties. Microwave treatment in standard domestic ovens results in hot and cold spots, and the microwaves do not penetrate all areas of the samples depending on the thickness, which makes it difficult to compare microwave with conventional heat treatments. The viability of Anisakis simplex (isolated larvae and infected fish muscle) heated in a microwave oven with precise temperature control was compared with that of larvae heated in a water bath to investigate any additional effect of the microwaves. At a given temperature, less time was required to kill the larvae by microwaves than by heated water. Microwave treatment killed A. simplex larvae faster than did conventional cooking when the microwaves fully penetrated the samples and resulted in fewer changes in the fish muscle. However, the heat-stable allergen Ani s 4 was detected by immunohistochemistry in the fish muscle after both heat treatments, even at 70°C, suggesting that Ani s 4 allergens were released from the larvae into the surrounding tissue and that the tissues retained their allergenicity even after the larvae were killed by both heat treatments. Thus, microwave cooking will not render fish safe for individuals already sensitized to A. simplex heat-resistant allergens.

  2. Microwave heating of aqueous samples on a micro-optical-electro-mechanical system

    SciTech Connect

    Beer, Neil Reginald

    2016-04-12

    Apparatus for heating a sample includes a microchip; a microchannel flow channel in the microchip, the microchannel flow channel containing the sample; a microwave source that directs microwaves onto the sample for heating the sample; a wall section of the microchannel flow channel that receives the microwaves and enables the microwaves to pass through wall section of the microchannel flow channel, the wall section the microchannel flow channel being made of a material that is not appreciably heated by the microwaves; a carrier fluid within the microchannel flow channel for moving the sample in the microchannel flow channel, the carrier fluid being made of a material that is not appreciably heated by the microwaves; wherein the microwaves pass through wall section of the microchannel flow channel and heat the sample.

  3. Microwave heating of aqueous samples on a micro-optical-electro-mechanical system

    SciTech Connect

    Beer, Neil Reginald

    2015-03-03

    Apparatus for heating a sample includes a microchip; a microchannel flow channel in the microchip, the microchannel flow channel containing the sample; a microwave source that directs microwaves onto the sample for heating the sample; a wall section of the microchannel flow channel that receives the microwaves and enables the microwaves to pass through wall section of the microchannel flow channel, the wall section the microchannel flow channel being made of a material that is not appreciably heated by the microwaves; a carrier fluid within the microchannel flow channel for moving the sample in the microchannel flow channel, the carrier fluid being made of a material that is not appreciably heated by the microwaves; wherein the microwaves pass through wall section of the microchannel flow channel and heat the sample.

  4. Experimental Evidence of Selective Heating of Molecules Adsorbed in Nanopores under Microwave Radiation

    SciTech Connect

    Jobic, H; Santander, Julian; Conner, Jr, W C; Wittaker, G; Giriat, G.; Harrison, A; Ollivier, J; Auerbach, Scott M

    2011-04-14

    We have performed in situ quasielastic neutron scattering (QENS) measurements on zeolite-guest systems under microwave irradiation, for comparison with corresponding simulations. Both experiment and simulation reveal selective heating of methanol in silicalite, but little to no heating of benzene in silicalite. Effective translational and rotational temperatures extracted from QENS data under microwave heating were found to depend on microwave power. In agreement with simulation, QENS rotational temperatures significantly exceed translational ones at high microwave power, thus providing the first microscopic proof for athermal effects in microwave-driven nanopores.

  5. Microwave thermal imaging of scanned focused ultrasound heating: animal experiments

    NASA Astrophysics Data System (ADS)

    Zhou, Tian; Meaney, Paul M.; Hoopes, P. Jack; Geimer, Shireen D.; Paulsen, Keith D.

    2011-03-01

    High intensity focused ultrasound (HIFU) uses focused ultrasound beams to ablate localized tumors noninvasively. Multiple clinical trials using HIFU treatment of liver, kidney, breast, pancreas and brain tumors have been conducted, while monitoring the temperature distribution with various imaging modalities such as MRI, CT and ultrasound. HIFU has achieved only minimal acceptance partially due to insufficient guidance from the limited temperature monitoring capability and availability. MR proton resonance frequency (PRF) shift thermometry is currently the most effective monitoring method; however, it is insensitive in temperature changes in fat, susceptible to motion artifacts, and is high cost. Exploiting the relationship between dielectric properties (i.e. permittivity and conductivity) and tissue temperature, in vivo dielectric property distributions of tissue during heating were reconstructed with our microwave tomographic imaging technology. Previous phantom studies have demonstrated sub-Celsius temperature accuracy and sub-centimeter spatial resolution in microwave thermal imaging. In this paper, initial animal experiments have been conducted to further investigate its potential. In vivo conductivity changes inside the piglet's liver due to focused ultrasound heating were observed in the microwave images with good correlation between conductivity changes and temperature.

  6. Effect of microwave-assisted heating on chalcopyrite leaching of kinetics, interface temperature and surface energy

    NASA Astrophysics Data System (ADS)

    Wen, Tong; Zhao, Yunliang; Xiao, Qihang; Ma, Qiulin; Kang, Shichang; Li, Hongqiang; Song, Shaoxian

    The microwave-assisted leaching was a new approach to intensify the copper recovery from chalcopyrite by hydrometallurgy. In this work, the effect of microwave-assisted heating on chalcopyrite leaching of kinetics, interfacial reaction temperature and surface energy were investigated. The activation energy of chalcopyrite leaching was affected indistinctively by the microwave-assisted heating (39.1 kJ/mol) compared with the conventional heating (43.9 kJ/mol). However, the boiling point of the leaching system increased through microwave-assisted heating. Because of the improved boiling point and the selective heating of microwave, the interfacial reaction temperature increased significantly, which gave rise to the increase of the leaching recovery of copper. Moreover, the surface energy of the chalcopyrite through microwave-assisted heating was also enhanced, which was beneficial to strengthen the leaching of chalcopyrite.

  7. Progress on conformal microwave array applicators for heating chestwall disease

    NASA Astrophysics Data System (ADS)

    Stauffer, P. R.; Maccarini, P. F.; Juang, T.; Jacobsen, S. K.; Gaeta, C. J.; Schlorff, J. L.; Milligan, A. J.

    2007-02-01

    Previous studies have reported the computer modeling, CAD design, and theoretical performance of single and multiple antenna arrays of Dual Concentric Conductor (DCC) square slot radiators driven at 915 and 433 MHz. Subsequently, practical CAD designs of microstrip antenna arrays constructed on thin and flexible printed circuit board (PCB) material were reported which evolved into large Conformal Microwave Array (CMA) sheets that could wrap around the surface of the human torso for delivering microwave energy to large areas of superficial tissue. Although uniform and adjustable radiation patterns have been demonstrated from multiple element applicators radiating into simple homogeneous phantom loads, the contoured and heterogeneous tissue loads typical of chestwall recurrent breast cancer have required additional design efforts to achieve good coupling and efficient heating from the increasingly larger conformal array applicators used to treat large area contoured patient anatomy. Thus recent work has extended the theoretical optimization of DCC antennas to improve radiation efficiency of each individual aperture and reduce mismatch reflections, radiation losses, noise, and cross coupling of the feedline distribution network of large array configurations. Design improvements have also been incorporated into the supporting bolus structure to maintain effective coupling of DCC antennas into contoured anatomy and to monitor and control surface temperatures under the entire array. New approaches for non-invasive monitoring of surface and sub-surface tissue temperatures under each independent heat source are described that make use of microwave radiometry and flexible sheet grid arrays of thermal sensors. Efforts to optimize the clinical patient interface and move from planar rectangular shapes to contoured vest applicators that accommodate entire disease in a larger number of patients are summarized. By applying heat more uniformly to large areas of contoured anatomy

  8. Thawing of Frozen Dressed Tuna by Microwave Heating

    NASA Astrophysics Data System (ADS)

    Tanaka, Takeo; Nagasaki, Tasuku; Takahashi, Kenji

    Large sized frozen yellowfin tuna and southern bluefin tuna in dressed form (decapitated and gutted) were thawed by microwave (915 MHz) irradiation. Temperature rise of the tuna during thawing was measured. Quality of the tuna meat before and after thawing was compared with each other using objective quality index such as degree of discoloration (met-myoglobin ratio), freshness (K1 value) and taste cornponent (K2 value). Results are as follows : (1) Both frozen tunas were thawed fairly well within as short time as 30 min without any partial over heating. (2) No changes in met-myoglobin ratio, K1 and K2 values were observed in the cases of yellow fin tuna. Slight discoloration, however, occurred in southern bluefin tuna meat during microwave thawing. This problem has been left unsolved.

  9. Mechanism for microwave heating of 1-(4'-cyanophenyl)-4-propylcyclohexane characterized by in situ microwave irradiation NMR spectroscopy.

    PubMed

    Tasei, Yugo; Yamakami, Takuya; Kawamura, Izuru; Fujito, Teruaki; Ushida, Kiminori; Sato, Motoyasu; Naito, Akira

    2015-05-01

    Microwave heating is widely used to accelerate organic reactions and enhance the activity of enzymes. However, the detailed molecular mechanism for the effect of microwave on chemical reactions is not yet fully understood. To investigate the effects of microwave heating on organic compounds, we have developed an in situ microwave irradiation NMR spectroscopy. (1)H NMR spectra of 1-(4'-cyanophenyl)-4-propylcyclohexane (PCH3) in the liquid crystalline and isotropic phases were observed under microwave irradiation. When the temperature was regulated at slightly higher than the phase transition temperature (Tc=45 °C) under a gas flow temperature control system, liquid crystalline phase mostly changed to the isotropic phase. Under microwave irradiation and with the gas flow temperature maintained at 20 °C, which is 25 °C below the Tc, the isotropic phase appeared stationary as an approximately 2% fraction in the liquid crystalline phase. The temperature of the liquid crystalline state was estimated to be 38 °C according to the line width, which is at least 7 °C lower than the Tc. The temperature of this isotropic phase should be higher than 45 °C, which is considered to be a non-equilibrium local heating state induced by microwave irradiation. Microwaves at a power of 195 W were irradiated to the isotropic phase of PCH3 at 50 °C and after 2 min, the temperature reached 220 °C. The temperature of PCH3 under microwave irradiation was estimated by measurement of the chemical shift changes of individual protons in the molecule. These results demonstrate that microwave heating generates very high temperature within a short time using an in situ microwave irradiation NMR spectrometer.

  10. Microwave heating behavior and microwave absorption properties of barium titanate at high temperatures

    NASA Astrophysics Data System (ADS)

    Kashimura, K.; Sugawara, H.; Hayashi, M.; Mitani, T.; Shinohara, N.

    2016-06-01

    The temperature dependence of the microwave absorption behavior of BaTiO3 particles was investigated over various frequencies and temperatures of 25-1000 ∘C. First, using both the coaxial transmission line method and the cavity perturbation method by a network analyzer, the real and imaginary parts of the relative permittivity of BaTiO3 ( ɛr ' and ɛr ″ , respectively) were measured, in order to improve the reliability of the data obtained at 2.45 GHz. The imaginary parts of the relative permittivity as measured by the two methods were explored by their heating behaviors. Furthermore, the temperature dependence of the microwave absorption behavior of BaTiO3 particles was investigated for frequencies of 2.0-13.5 GHz and temperatures of 25-1000 ∘C using the coaxial transmission line method.

  11. Microwave sensing and heating of individual droplets in microfluidic devices.

    PubMed

    Boybay, Muhammed S; Jiao, Austin; Glawdel, Tomasz; Ren, Carolyn L

    2013-10-07

    Droplet-based microfluidics is an emerging high-throughput screening technology finding applications in a variety of areas such as life science research, drug discovery and material synthesis. In this paper we present a cost-effective, scalable microwave system that can be integrated with microfluidic devices enabling remote, simultaneous sensing and heating of individual nanoliter-sized droplets generated in microchannels. The key component of this microwave system is an electrically small resonator that is able to distinguish between materials with different electrical properties (i.e. permittivity, conductivity). The change in these properties causes a shift in the operating frequency of the resonator, which can be used for sensing purposes. Alternatively, if microwave power is delivered to the sensing region at the frequency associated with a particular material (i.e. droplet), then only this material receives the power while passing the resonator leaving the surrounding materials (i.e. carrier fluid and chip material) unaffected. Therefore this method allows sensing and heating of individual droplets to be inherently synchronized, eliminating the need for external triggers. We confirmed the performance of the sensor by applying it to differentiate between various dairy fluids, identify salt solutions and detect water droplets with different glycerol concentrations. We experimentally verified that this system can increase the droplet temperature from room temperature by 42 °C within 5.62 ms with an input power of 27 dBm. Finally we employed this system to thermally initiate the formation of hydrogel particles out of the droplets that are being heated by this system.

  12. The Analysis of Parametric Sensitivity Based on Designing and Optimization of a New Microwave Heating System

    NASA Astrophysics Data System (ADS)

    Chen, Hua; Zhang, Jin; Fan, Zebin; Peng, Jinhui; Ju, Shaohua

    2017-09-01

    Microwave-assisted heating technology has become a popular alternative to conventional heating technologies because of its many advantages. However, the matching performance of microwave heating system is of particular concern because it provides an important index of the utilization efficiency of microwave energy. In this work, a new microwave heating system is designed by the theory of optical resonator in first. Then the comprehensive analysis of the mutual coupling of high sensitive geometrical and material parameters were investigated based on this new microwave heating system at 2.45 GHz. It is demonstrated that the thickness of materials dramatically influences microwave energy absorption efficiency and should be carefully considered and perhaps given priority. Moreover, it is shown that matching performance is the best when the titanium concentrates thickness at about 0.075 m.

  13. Behavioral observations and operant procedures using microwaves as a heat source for young chicks

    SciTech Connect

    Morrison, W.D.; McMillan, I.; Bate, L.A.; Otten, L.; Pei, D.C.

    1986-08-01

    Four trials, using operant conditioning procedures, were conducted to study the response of chicks, housed at 16 C, to microwave or infrared heat. Microwave power density was 26 mW/cm2 in Trial 1, 13 mW/cm2 in Trial 2, and 10 mW/cm2 in Trials 3 and 4. Chicks voluntarily demanded between 28 and 63% as much heat (min heat/hr) from microwave source as from infrared source at all power densities. There was no correlation, however, between the ratio of heat demanded and the power density used. There were no significant differences in growth between infrared- or microwave-heated chicks. It is evident from these studies that 8-day-old broiler chicks are capable of associating the performance of a task with a thermal reward provided by the microwaves. They are also able to utilize these microwaves through operant conditioning without any visible detrimental effect to their health or behavior.

  14. Multichannel infrared fiber optic radiometer for controlled microwave heating

    NASA Astrophysics Data System (ADS)

    Drizlikh, S.; Zur, Albert; Katzir, Abraham

    1990-07-01

    An infrared fiberoptic multichannel radiometer was used for monitoring and controlling the temperature of samples in a microwave heating system. The temperature of water samples was maintained at about 40 °C, with a standard deviation of +/- 0.2°C and a maximum deviation of +/- 0.5°C. The temperature was monitored on the same time at several points on the surface and inside the sample. This novel controlled system is reliable and precise. Such system would be very useful for medical applications such as hypothermia and hyperthermi a.

  15. The catalytic pyrolysis of food waste by microwave heating.

    PubMed

    Liu, Haili; Ma, Xiaoqian; Li, Longjun; Hu, ZhiFeng; Guo, Pingsheng; Jiang, Yuhui

    2014-08-01

    This study describes a series of experiments that tested the use of microwave pyrolysis for treating food waste. Characteristics including rise in temperature, and the three-phase products, were analyzed at different microwave power levels, after adding 5% (mass basis) metal oxides and chloride salts to the food waste. Results indicated that, the metal oxides MgO, Fe₂O₃ and MnO₂ and the chloride salts CuCl₂ and NaCl can lower the yield of bio-oil and enhance the yield of gas. Meanwhile, the metal oxides MgO and MnO₂ can also lower the low heating value (LHV) of solid residues and increase the pH values of the lower layer bio-oils. However, the chloride salts CuCl₂ and NaCl had the opposite effects. The optimal microwave power for treating food waste was 400W; among the tested catalysts, CuCl₂ was the best catalyst and had the largest energy ratio of production to consumption (ERPC), followed by MnO₂. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Microwave heating and joining of ceramic cylinders: A mathematical model

    NASA Technical Reports Server (NTRS)

    Booty, Michael R.; Kriegsmann, Gregory A.

    1994-01-01

    A thin cylindrical ceramic sample is placed in a single mode microwave applicator in such a way that the electric field strength is allowed to vary along its axis. The sample can either be a single rod or two rods butted together. We present a simple mathematical model which describes the microwave heating process. It is built on the assumption that the Biot number of the material is small, and that the electric field is known and uniform throughout the cylinder's cross-section. The model takes the form of a nonlinear parabolic equation of reaction-diffusion type, with a spatially varying reaction term that corresponds to the spatial variation of the electromagnetic field strength in the waveguide. The equation is analyzed and a solution is found which develops a hot spot near the center of the cylindrical sample and which then propagates outwards until it stabilizes. The propagation and stabilization phenomenon concentrates the microwave energy in a localized region about the center where elevated temperatures may be desirable.

  17. Microwave heat treatment of natural ruby and its characterization

    NASA Astrophysics Data System (ADS)

    Swain, S.; Pradhan, S. K.; Jeevitha, M.; Acharya, P.; Debata, M.; Dash, T.; Nayak, B. B.; Mishra, B. K.

    2016-03-01

    Natural ruby (in the form of gemstone) collected from Odisha has been heat-treated by microwave (MW). A 3-kW industrial MW furnace with SiC susceptors was used for the heat treatment. The ruby samples showed noticeable improvements (qualitative), may be attributed to account for the improvement in clarity and lustre. Optical absorption in 200-800 nm range and photoluminescence peak at 693 nm (with 400 nm λ ex) clearly show that subtle changes do take place in the ruby after the heat treatment. Further, inorganic compound phases and valence states of elements (impurities) in the ruby were studied by X-ray diffraction, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The valence states of the main impurities such as Cr, Fe, and Ti, in the untreated and MW heat-treated ruby, as revealed from XPS, have been discussed in depth. The overall results demonstrate for the first time the effect of fast heating like MW on the microstructural properties of the gemstone and various oxidation states of impurity elements in the natural ruby.

  18. Influence of microwave heating on biogas production from Sida hermaphrodita silage.

    PubMed

    Zieliński, Marcin; Dębowski, Marcin; Rusanowska, Paulina

    2017-09-01

    This study compared the effects on biogas production of suspended sludge versus a combination of suspended sludge and immobilized biomass, and microwave versus convection heating. Biogas production was the highest in the hybrid bioreactor heated by microwaves (385L/kg VS) and also the most stable, as shown by the FOS/TAC ratio and pH. Regardless of the type of heating, biogas production was 8% higher with immobilized biomass than without. Although the lag phase of biogas production was shorter with microwave heating than without, the log phase was longer, and biogas production in the microwave heated bioreactors took about twice as long (ca. 40days) to plateau as in the conventionally heated bioreactors. These differences in the profile of biogas production are likely due to the athermal effects of microwave irradiation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Method for heat treating and sintering metal oxides with microwave radiation

    DOEpatents

    Holcombe, Cressie E.; Dykes, Norman L.; Meek, Thomas T.

    1989-01-01

    A method for microwave sintering materials, primarily metal oxides, is described. Metal oxides do not normally absorb microwave radiation at temperatures ranging from about room temperature to several hundred degrees centrigrade are sintered with microwave radiation without the use of the heretofore required sintering aids. This sintering is achieved by enclosing a compact of the oxide material in a housing or capsule formed of a oxide which has microwave coupling properties at room temprature up to at least the microwave coupling temperature of the oxide material forming the compact. The heating of the housing effects the initial heating of the oxide material forming the compact by heat transference and then functions as a thermal insulator for the encased oxide material after the oxide material reaches a sufficient temperature to adequately absorb or couple with microwave radiation for heating thereof to sintering temperature.

  20. Determining the effects of microwave heating on the ordered structures of rice starch by NMR.

    PubMed

    Fan, Daming; Ma, Wenrui; Wang, Liyun; Huang, Jianlian; Zhang, Fengmin; Zhao, Jianxin; Zhang, Hao; Chen, Wei

    2013-02-15

    The effects of microwave heating on the double helices, single helix and amorphous structures and the relative crystallinity of rice starch were studied by (13)C CP/MAS NMR method, with rapid heating in an oil bath and conventional slow heating as controls. The results indicated that compared with rapid heating, microwave heating did not significantly change the ordered and disordered structures. All of the heating methods exhibited similar content changes to the double helices, V-type single helix and amorphous structures with rising temperature. The rapid heating effects caused by microwave and oil bath accelerated the destruction of the V-type single helix in the starch granules. The electromagnetic effect of microwave heating did not affect the decrease of the double helices or the amorphous content of the starch.

  1. Modification of bactericidal effects of microwave heating and hyperthermia by hydrogen peroxide.

    PubMed

    Kuchma, T

    1997-01-01

    Two different approaches for studying of bactericidal effects of microwave heating and hyperthermia were introduced. Low concentration of hydrogen peroxide (0.05%) was used to modify the sensitivity of isogenous strains of Escherichia coli K-12 to microwave heating and hyperthermia with the following assessment of their combined action. This was carried out simulataneously and successively under equal conditions of temperature rise at 50 degrees C. A method of anomalous viscosity time dependencies (AVTD) was used for measurement of the changes in genome conformational state simultaneously with bacterial survival determination. Experiments were performed to study isolated effects of hyperthermia and microwave heating over a range of temperatures from 40 to 80 degrees C and hydrogen peroxide concentrations from 0.05 to 0.3% during 10-minute exposures and their combined action. No difference was found between isolated effects of microwave heating and hyperthermia when survival of E. coli AB 1157 cells was determined. It was shown by the AVTD method that microwave heating at a temperature increase of 6 degrees C per second caused greater damage to cell genome than hyperthermia. The synergistic interaction of microwave heating and low concentrations of hydrogen peroxide was found in simulataneous and successive exposures. The essential distinctions observed in recognition of the action of microwave heating and hyperthermia combined with hydrogen peroxide in various sequences on cellular and molecular levels were attributed to the different effects of microwave and conventional heating on the systems of DNA repair.

  2. 21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Radiofrequency radiation for the heating of food... FOOD Radiation and Radiation Sources § 179.30 Radiofrequency radiation for the heating of food, including microwave frequencies. Radiofrequency radiation, including microwave frequencies, may be safely...

  3. The Study of New Technology of Tempered Glass--Using Microwave Heating Method

    NASA Astrophysics Data System (ADS)

    Sun, Wan-Xiao; Wang, Li-Zhong; Zhong, Pei-Ze; Liu, Quan-Wei

    2016-05-01

    Effective heating method is one of the critical technologies to influence the quality of tempered glass. The three dimensional thermal-structural tempering of glass has been simulated by using ANSYS software. The temperature and stress distribution of tempered glass using microwave heating method has been compared with distribution using traditional infrared radiation heating method. Considering the efficiency and effect of heating, and the routine of increasing heat transfer coefficient to enhance strength of tempered glass in practical, a more effective heating method -microwave heating has been introduced.

  4. Factors affecting the catalytic oligomerization of methane via microwave heating

    NASA Astrophysics Data System (ADS)

    Conde, Luis Daniel

    Catalytic microwave heating has been used as a method for the oligomerization of methane to higher hydrocarbons. Many catalysts were tested in this reaction. Nickel powder, raney nickel, iron powder and activated carbon were the most active and efficient catalysts for the production of higher hydrocarbons. When helium was used as a diluent gas and the applied power was optimized, the selectivities were controlled to the most desired products. In general, the most abundant products for all the experiments were C2s. Iron powder was active only at high power (1130 W). At these conditions acetylene was avoided and ethylene and ethane were produced in the same proportion. Activated carbon catalysts with helium as diluent led to a selectivity towards benzene up to 33%. Some manganese oxides such as OMS-1, OMS-2 and MnO2 (dielectric constant, epsilon ≈ 104) were not active in these reactions. These data suggest that the dielectric constant is not the most important factor in the oligomerization of methane via microwave heating. Conversion and activities of these materials are not proportionally related to the surface area of the catalysts. Higher catalytic activity was observed for Raney nickel than for regular nickel powder. The maximum conversion obtained was 24% at 400 W and 10 min of irradiation time. For regular nickel powder that conversion can be achieved only after 700 W of power and more than 20 min of reaction. BET surface area, Scanning Electron Microscopy, X-ray Photoelectron Spectroscopy, and Temperature-Programmed Desorption and Reduction analysis were performed to characterize the catalyst before and after reaction. Deactivation of Raney nickel by fouling and sintering was observed after 500 W and/or 15 min of reaction. The effect of microwave radiation frequency on activity and product distribution for methane oligomerization has been studied. Nickel, iron, and activated carbon catalysts were used in these studies. Experiments were done with pure methane

  5. Migration of DEHP from plastic to food simulants under microwave heating

    NASA Astrophysics Data System (ADS)

    Zhu, X.; Li, F.; Qiu, Z. Z.; Huang, J. W.

    2017-05-01

    The migration of plasticizer DEHP from the plastic products (4 kinds of commonly used plastic food containers under microwave heating: plastic wrap, food bags, ordinary plastic boxes, microwave special plastic boxes) through food contact materials to food simulants (isooctane, 10% ethanol-water solution (v/v), 3% acetic acid-water solution (w/w) and distilled water) was studied under microwave heating (power levels of 400 W). The results shows that the DEHP mobility increases with the increase of microwave heating time, DEHP mobility in isooctane and 3% acetic acid-water solution (w/w) is significantly greater than in 10% ethanol-water solution (v/v) and distilled water; the order of DEHP mobility in isooctane is plastic wrap>food bag>common plastic box>microwave-safe plastic box, while in 3% acetic acid (w/w), the order is food bag>common plastic box>microwave-safe plastic box>plastic wrap.

  6. Microwave design and analysis of a micromachined self-heating power sensor based on matching thermocouples

    NASA Astrophysics Data System (ADS)

    Zhang, Zhiqiang; Liao, Xiaoping

    2017-08-01

    Microwave performance is a basic index of the sensors used at microwave frequencies, but also affects the sensing output. For the purpose of low-loss microwave applications, it is important for different microwave sensors to develop microwave design. This paper presents the microwave design and analysis of a micromachined self-heating microwave power sensor in the GaAs MMIC process, where the microwave power is dissipated and converted into output thermovoltages by two matching thermocouples. A dc-blocking capacitor is connected to the thermocouples in series and used to avoid the output short-circuit. In order to characterize the microwave performance, an S-parameter model of this self-heating power sensor is established. Using the model, the effects of the capacitor and the thermocouples on the reflection loss are investigated under different microwave frequencies. To demonstrate the validity of the microwave model, the microwave performance of the self-heating sensor is simulated using an electromagnetic software. In the simulation, the relationship between the substrate membrane underneath the thermocouples and the reflection loss is analyzed. Measured reflection losses of the self-heating sensor are between  -15.5 to  -15.9 dB at 8-12 GHz. The measured results show good agreement with the microwave model and simulation, and the source of small deviations is discussed. The proposed microwave design and analysis contributes to achieving low reflection loss for the sensor, with the fact that more power is used to convert into the thermovoltages.

  7. Microstructural and mechanical properties of camel longissimus dorsi muscle during roasting, braising and microwave heating.

    PubMed

    Yarmand, M S; Nikmaram, P; Djomeh, Z Emam; Homayouni, A

    2013-10-01

    This study was conducted to investigate the effects of various heating methods, including roasting, braising and microwave heating, on mechanical properties and microstructure of longissimus dorsi (LD) muscle of the camel. Shear value and compression force increased during microwave heating more than roasting and braising. Results obtained from scanning electron microscopy (SEM) showed more damage from roasting than in either braising or microwave heating. Granulation and fragmentation were clear in muscle fibers after roasting. The perimysium membrane of connective tissue was damaged during braising, while roasting left the perimysium membrane largely intact. The mechanical properties and microstructure of muscle can be affected by changes in water content during cooking.

  8. A comparison of microwave versus direct solar heating for lunar brick production

    NASA Technical Reports Server (NTRS)

    Yankee, S. J.; Strenski, D. G.; Pletka, B. J.; Patil, D. S.; Mutsuddy, B. C.

    1990-01-01

    Two processing techniques considered suitable for producing bricks from lunar regolith are examined: direct solar heating and microwave heating. An analysis was performed to compare the two processes in terms of the amount of power and time required to fabricate bricks of various sizes. Microwave heating was shown to be significantly faster than solar heating for rapid production of realistic-size bricks. However, the relative simplicity of the solar collector(s) used for the solar furnace compared to the equipment necessary for microwave generation may present an economic tradeoff.

  9. Observation of localized heating phenomena during microwave heating of mixed powders using in situ x-ray diffraction technique

    SciTech Connect

    Sabelström, N. Hayashi, M.; Watanabe, T.; Nagata, K.

    2014-10-28

    In materials processing research using microwave heating, there have been several observations of various phenomena occurring known as microwave effects. One significant example of such a phenomenon is increased reaction kinetics. It is believed that there is a possibility that this might be caused by localized heating, were some reactants would attain a higher than apparent temperature. To examine whether such thermal gradients are indeed possible, mixed powders of two microwave non-absorbers, alumina and magnesia, were mixed with graphite, a known absorber, and heated in a microwave furnace. During microwave irradiation, the local temperatures of the respective sample constituents were measured using an in situ x-ray diffraction technique. In the case of the alumina and graphite sample, a temperature difference of around 100 °C could be observed.

  10. Validation of measured microwave absorption and temperature change for development of a single-mode-type microwave heating thermogravimetry apparatus

    NASA Astrophysics Data System (ADS)

    Karisma, Achmad Dwitama; Hamaba, Taishu; Fukasawa, Tomonori; Huang, An-Ni; Segawa, Tomoomi; Fukui, Kunihiro

    2017-02-01

    The temperature distribution, microwave absorption efficiency, and dielectric properties of a copper (ii) oxide (CuO) pellet heated by microwave irradiation were investigated for use in developing a single-mode-type microwave heating thermogravimetry apparatus. The validity of the apparatus was confirmed by comparing the measured data with the results of numerical simulations. The dielectric properties and error margins of other parameters estimated using the apparatus were also examined. The temperature distribution of the CuO pellet was observed to decrease monotonously on moving from the outlet to the inlet side of the apparatus. A three-dimensional numerical simulation of the electromagnetic field accurately reproduced this temperature distribution, suggesting the one-way movement of microwaves in the single-mode-type microwave apparatus. The numerically determined dependency of the CuO absorption efficiency was also found to be in very good agreement with published data. The same was the case with the permittivity loss of the CuO at various temperatures, as estimated from the measured microwave absorption efficiency. However, a larger error was observed in the estimation of the permittivity loss of a material with a lower microwave absorption efficiency, which was apparently due to the measurement error of the absorption efficiency of such a material.

  11. Electron Heating in Microwave-Assisted Helicon Plasmas

    NASA Astrophysics Data System (ADS)

    McKee, John; Siddiqui, Umair; Jemiolo, Andrew; McIlvain, Julianne; Scime, Earl

    2016-10-01

    The use of two (or more) rf sources at different frequencies is a common technique in the plasma processing industry to control ion energy characteristics separately from plasma generation. A similar approach is presented here with the focus on modifying the electron population in argon and helium plasmas. The plasma is generated by a helicon source at a frequency f 0 = 13.56 MHz. Mcrowaves of frequency f 1 = 2.45 GHz are then injected into the helicon source chamber perpendicular to the background magnetic field. The microwaves damp on the electrons via X-mode Electron Cyclotron Heating (ECH) at the upper hybrid resonance, providing additional energy input into the electrons. The effects of this secondary-source heating on electron density, temperature, and energy distribution function are examined and compared to helicon-only single source plasmas as well as numeric models suggesting that the heating is not evenly distributed but spatially localized. Optical Emission Spectroscopy (OES) is used to examine the impact of the energetic tail of the electron distribution on ion and neutral species via collisional excitation. Large enhancements of neutral spectral lines are observed with little to no enhancement of ion lines.

  12. Microwave heating: Industrial applications. (Latest citations from the NTIS bibliographic database). Published Search

    SciTech Connect

    1995-12-01

    The bibliography contains citations concerning industrial uses and design of microwave heating equipment. Included are heating and drying of paper, industrial process heat, vulcanization, textile processing, metallurgical heat for sintering and ceramic manufacturing, food processing, and curing of polymers.(Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  13. Microwave-specific heating of crystalline species in nuclear waste glass

    DOE PAGES

    Christian, Jonathan H.; Fox, Kevin M.; Washington, Aaron L.

    2016-08-03

    Here, the microwave heating of a crystal-free and a partially trevorite-crystallized nuclear waste glass simulant was evaluated. Our results show that a 500-mg monolith of partially crystallized waste glass can be heated from room temperature to above 1600°C within 2 min using a single-mode, highly focused, 2.45 GHz microwave, operating at 300 W. Using X-ray diffraction measurements, we show that trevorite is no longer detectable after irradiation and thermal quenching. When a crystal-free analog of the same waste glass simulant composition was exposed to the same microwave radiation, it could not be heated above 450°C regardless of the heating time.more » The reduction in crystalline content achieved by selectively heating spinels in the presence of glass suggests that microwave-specific heating should be further explored as a technique for remediating crystal accumulation in a glass melt.« less

  14. Microwave-specific heating of crystalline species in nuclear waste glass

    SciTech Connect

    Christian, Jonathan H.; Fox, Kevin M.; Washington, Aaron L.

    2016-08-03

    Here, the microwave heating of a crystal-free and a partially trevorite-crystallized nuclear waste glass simulant was evaluated. Our results show that a 500-mg monolith of partially crystallized waste glass can be heated from room temperature to above 1600°C within 2 min using a single-mode, highly focused, 2.45 GHz microwave, operating at 300 W. Using X-ray diffraction measurements, we show that trevorite is no longer detectable after irradiation and thermal quenching. When a crystal-free analog of the same waste glass simulant composition was exposed to the same microwave radiation, it could not be heated above 450°C regardless of the heating time. The reduction in crystalline content achieved by selectively heating spinels in the presence of glass suggests that microwave-specific heating should be further explored as a technique for remediating crystal accumulation in a glass melt.

  15. Infrared fiber optic temperature monitoring of biological tissues heated in a microwave oven

    NASA Astrophysics Data System (ADS)

    Belotserkovsky, Edward; Ashkenasy, Y.; Shenfeld, Ofer; Drizlikh, S.; Zur, Albert; Katzir, Abraham

    1993-05-01

    The heating of tissue by microwave radiation has attained a place of importance in various medical fields such as the treatment of malignancies, urinary retention and hypothermia. Accurate temperature measurements in these treated tissues is important for treatment planning and for the control of the heating process. It is also important to be able to measure spacial temperature distribution in the tissues because they are heated in a non uniform way by the microwave radiation. Fiber optic radiometry makes possible accurate temperature measurement in the presence of microwave radiation and does not require contact with the tissue. Using a IR silver halide fiber optic radiometric temperature sensor we obtained accurate temperature measurements of tissues heated by microwave, enabling us to control the heating process in all regions of the tissue. We also performed temperature mapping of the heated tissues and demonstrated the non-uniform temperature distributions in them.

  16. Geometry for web microwave heating or drying to a desired profile in a waveguide

    DOEpatents

    Habeger, Jr., Charles C.; Patterson, Timothy F.; Ahrens, Frederick W.

    2005-11-15

    A microwave heater and/or dryer has a nonlinear or curvilinear relative slot profile geometry. In one embodiment, the microwave dryer has at least one adjustable field modifier making it possible to change the geometry of the heater or dryer when drying different webs. In another embodiment, the microwave dryer provides more uniform drying of a web when the field modifier is adjusted in response to a sensed condition of the web. Finally, a method of microwave heating and/or drying a web achieves a uniform heating and/or drying profile.

  17. Silicon heating by a microwave-drill applicator with optical thermometry

    NASA Astrophysics Data System (ADS)

    Herskowits, R.; Livshits, P.; Stepanov, S.; Aktushev, O.; Ruschin, S.; Jerby, E.

    2007-08-01

    This paper presents a method for heating silicon wafers locally by open-end coaxial microwave applicators, with optical techniques employed for measuring the temperature. Silicon samples of ~2 × 2 cm2 area were radiated in air atmosphere by a microwave drill operating at 2.45 GHz in the range of 20-450 W. The rate of temperature variation was measured by the Fabry-Pérot etalon effect in samples illuminated by InGaAs lasers. The steady-state temperatures were measured by the changes in the absorption index of an InGaAs laser beam. The experimental results indicate heating rates of ~150 K s-1 and a temperature range of 300-900 K across the silicon sample during the microwave heating process. Further operation of the microwave drill caused local melting of the silicon samples. This paper presents the experimental setup and results, as well as numerical simulations of the microwave heating process.

  18. Adjustments in metabolic heat production by squirrel monkeys exposed to microwaves

    SciTech Connect

    Adair, E.R.; Adams, B.W.

    1982-04-01

    The basic fact that microwave exposure can lower metabolic heat production has been previously demonstrated for the mouse by Ho and Edwards (1977) and for the rat by Phillips et al. (1975). The general conclusion drawn from both studies was that the metabolic reduction produced by microwave exposure was dose dependent. The present study extends the investigation into the effects of microwave exposure on metabolic heat production to a primate, the squirrel monkey. When squirrel monkeys are restrained in cool environments, body temperature is regulated by an increase in metabolic heat production. The results of the current study demonstrate that either brief or prolonged whole-body exposure to a microwave field will cause a reduction of this elevated heat production by an amount directly related to the microwave energy absorbed.

  19. Synthesis of silicon carbide nanowhiskers by microwave heating: effect of heating duration

    NASA Astrophysics Data System (ADS)

    Kahar, S. M.; Voon, C. H.; Lee, C. C.; Gopinath, S. C. B.; Arshad, M. K. Md; Lim, B. Y.; Foo, K. L.; Hashim, U.

    2017-01-01

    SiC nanowhiskers (SiCNWs), due to their unique properties such as high thermal stability, high strength, high thermal conductivity and large band gap, lead to a wide range of applications. In this article, synthesis of SiCNWs was performed by using microwave heating. Silica and graphite in the ratio of 1:3 were mixed in an ultrasonic bath, dried on a hotplate and cold pressed uniaxially into a pellet die. The pellets were heated by using a laboratory microwave furnace to 1400 °C with a heating rate of 20 °C min-1 and heated for 20, 40 and 60 min. Characterizations of the as synthesized SiCNWs were done to study the effect of heating duration on the morphology and properties of SiCNWs. A time of 40 min was found to be the most ideal heating duration for the synthesis of SiCNWs. β-SiC appeared as the only phase in the x-ray diffraction pattern for SiCNWs formed by using 40 and 60 min of heating duration with no traces of unreacted silica and graphite. Field emission scanning electron microscopy imaging confirmed that no trace of graphite or silica was present in SiCNWs synthesized by a heating duration of 40 and 60 min. Energy dispersive x-ray spectroscopy analysis revealed that only elemental C and Si were present for SiCNWs synthesized at 40 and 60 min. Meanwhile, photoluminescence spectroscopy indicated the presence of single phase β-SiC peak at 440 nm was associated with band gap of 2.8 eV. Absorption bands of Si-C bond were detected at 802.4 cm-1 in the spectra of fourier transform infrared analysis. SiCNWs produced by heating at 40 and 60 min have high thermal stability with weight loss lower than 6%. A simple process that involved two steps of ultrasonic mixing and microwave heating of graphite and SiO2 is proposed as a new route for the synthesis of SiCNWs.

  20. A comparison of direct heating during radiofrequency and microwave ablation in ex vivo liver

    PubMed Central

    Andreano, Anita; Brace, Christopher L

    2012-01-01

    Purpose To determine the magnitude and spatial distribution of temperature elevations when using 480 kHz RF and 2.45 GHz microwave energy in ex vivo liver models. Materials and Methods A total of sixty heating cycles (20 s at 90 W) were performed in normal, RF ablated and microwave ablated liver tissues (n=10 RF and n=10 microwave in each tissue type). Heating cycles were performed using a 480 kHz generator and 3 cm cooled-tip electrode (RF) or a 2.45 GHz generator and 14-gauge monopole (microwave) and designed to isolate direct heating from each energy type. Tissue temperatures were measured using fiberoptic thermosensors 5, 10 and 15 mm radially from the ablation applicator at the depth of maximal heating. Power delivered, sensor location, heating rates and maximal temperatures were compared using mixed effects regression models. Results No significant differences were noted in mean power delivered or thermosensor locations between RF and microwave heating groups (P>0.05). Microwaves produced significantly more rapid heating than RF at 5, 10 and 15mm in normal tissue (3.0 vs. 0.73, 0.85 vs. 0.21 and 0.17 vs. 0.09 °C/s; P<.05); and at 5 and 10mm in ablated tissues (2.3 ± 1.4 vs. 0.7 ± 0.3, 0.5 ± 0.3 vs. 0.2 ± 0.0 C/s, P<.05). The radial depth of heating was approximately 5mm greater for microwaves than RF. Conclusions Direct heating obtained with 2.45 GHz microwave energy using a single needle-like applicator is faster and covers a larger volume of tissue than 480 kHz RF energy. Keywords: microwave ablation, direct heating, thermal ablation PMID:22572764

  1. Studying the effect of microwave heating on the digestion process and identification of proteins.

    PubMed

    Devi, Shobha; Wu, Bo-Hung; Chu, Pei-Yu; Liu, Yue-Pei; Wu, Hsin-Lin; Ho, Yen-Peng

    2017-02-01

    The impact of microwave irradiation on the in-solution digestion processes and the detection limit of proteins are systematically studied. Kinetic processes of many peptides produced through the trypsin digestion of various proteins under microwave heating at 50°C were investigated with MALDI-MS. This study also examines the detection limits and digestion completeness of individual proteins under microwave heating at 50°C and at different time intervals (1, 5 and 30 min) using LC-MS. We conclude that if the peptides without missed cleavage dictate the detection limit, conventional digestion will lead to a better detection limit. The detection limit may not differ between the microwave and conventional heating if the peptides with missed cleavage sites and strong intensity are formed at the very early stage (i.e., less than 1 min) and are not further digested throughout the entire digestion process. The digestion of Escherichia coli lysate was compared under conventional and short time (microwave) conditions. The number of proteins identified under conventional heating exceeded that obtained from microwave heating over heating periods less than 5 min. The overall results show that the microwave-assisted digestion is not complete. Although the sequence coverage might be better, the detection limit might be worse than that under conventional heating. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Thermal runaway and microwave heating in thin cylindrical domains

    NASA Astrophysics Data System (ADS)

    Ward, Michael J.

    2002-04-01

    The behaviour of the solution to two nonlinear heating problems in a thin cylinder of revolution of variable cross-sectional area is analysed using asymptotic and numerical methods. The first problem is to calculate the fold point, corresponding to the onset of thermal runaway, for a steady-state nonlinear elliptic equation that arises in combustion theory. In the limit of thin cylindrical domains, it is shown that the onset of thermal runaway can be delayed when a circular cylindrical domain is perturbed into a dumbell shape. Numerical values for the fold point for different domain shapes are obtained asymptotically and numerically. The second problem that is analysed is a nonlinear parabolic equation modelling the microwave heating of a ceramic cylinder by a known electric field. The basic model in a thin circular cylindrical domain was analysed in Booty & Kriegsmann (Meth. Appl. Anal. 4 (1994) p. 403). Their analysis is extended to treat thin cylindrical domains of variable cross-section. It is shown that the steady-state and dynamic behaviours of localized regions of high temperature, called hot-spots, depend on a competition between the maxima of the electric field and the maximum deformation of the circular cylinder. For a dumbell-shaped region it is shown that two disconnected hot-spot regions can occur. Depending on the parameters in the model, these regions, ultimately, either merge as time increases or else remain as disconnected regions for all time.

  3. Comparison of microwave and conduction-convection heating autohydrolysis pretreatment for bioethanol production.

    PubMed

    Aguilar-Reynosa, Alejandra; Romaní, Aloia; Rodríguez-Jasso, Rosa M; Aguilar, Cristóbal N; Garrote, Gil; Ruiz, Héctor A

    2017-06-20

    This work describes the application of two forms of heating for autohydrolysis pretreatment on isothermal regimen: conduction-convection heating and microwave heating processing using corn stover as raw material for bioethanol production. Pretreatments were performed using different operational conditions: residence time (10-50 min) and temperature (160-200°C) for both pretreatments. Subsequently, the susceptibility of pretreated solids was studied using low enzyme loads, and high substrate loads. The highest conversion was 95.1% for microwave pretreated solids. Also solids pretreated by microwave heating processing showed better ethanol conversion in simultaneous saccharification and fermentation process (92% corresponding to 33.8g/L). Therefore, microwave heating processing is a promising technology in the pretreatment of lignocellulosic materials. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Oro-facial thermal injury caused by food heated in a microwave oven.

    PubMed

    Wakefield, Yasha; Pemberton, Michael N

    2009-01-01

    Burns to the oral mucosa usually result from the accidental ingestion of hot food or beverages. The burns are usually of short duration and little consequence. The widespread use of microwave ovens, however, has added a new dimension to the problem. Microwave ovens heat food much quicker than a conventional oven, but they produce uneven heating within the food and extremely high temperatures can be reached. We describe two cases of patients who suffered inadvertent injury to the oral mucosa from the ingestion of microwave-heated food.

  5. Cumulative effect of microwave sterilization on the physical properties of microwave polymerized and conventional heat-polymerized acrylic resin

    PubMed Central

    Shafeeq, S. Mohammed; Karthikeyan, S.; Reddy, Subash M.; Karthigeyan, Suma; Manikandan, R.; Thangavelu, Arthiie

    2016-01-01

    Aims: To evaluate and compare the flexural strength and impact strength of conventional and microwave cured denture base resins before and after repeated sterilization using microwave energy to consider microwave curing as an alternative to the conventional method of sterilization. Materials and Methods: The conventional heat cure acrylic resin (DPI heat cure material) Group A and microwave-polymerized acrylic resin (Vipi Wave Acrylic resin) Group B were used to fabricate 100 acrylic resins samples using a standard metal die of (86 mm × 11 mm × 3 mm) dimensions. The criterion was flexural strength and impact strength testing which had Group A and Group B samples; 50 samples for flexural strength and 50 samples for impact strength measurement. For each criterion, five control samples were taken for Group A and Group B. The samples were stored in water before experimenting. The test samples were subject to four cycles of microwave sterilization; followed by flexural strength testing with a 3-point flexural test in universal testing machine (UNITEK 94100) and impact strength testing with impact testing machine (ENKAY Pr09/E1/16). Results: The physical properties had significant changes for conventionally cured denture base resins, whereas no changes found for microwave-cured resins after repeated sterilization cycles. PMID:27829757

  6. Effects of microwave heating on the migration of substances from melamine formaldehyde tableware.

    PubMed

    Poovarodom, Ngamtip; Junsrisuriyawong, Kansuda; Sangmahamad, Raweeporn; Tangmongkollert, Pattaree

    2014-01-01

    Melamine formaldehyde (MF) tableware, after undergoing repeated heating in a microwave oven for 1, 2, 3 or 5 min, was tested for migration into 3% (w/v) acetic acid, a food simulant. Overall migration (OM) consistently increased with an increasing number of heating/washing cycles, while formaldehyde was found at low concentrations or was not detectable. Unexpectedly, the 1-min series caused the most rapid increase in OM; the European Union regulatory limit of 10 mg dm(-2) was exceeded after 25 cycles. The number of cycles required to reach the OM limit rose to 29 and 67 for the 2- and 3-min series, respectively. Only 37 cycles were needed in the case of the 5-min series; however, the cumulative exposure time to microwave irradiation was relatively close to that of the 3-min series. These findings indicate that microwave heating affects the migration of MF in a significantly different manner as compared with conventional heating reported in previous studies. Fourier transform infrared spectroscopy (FTIR) spectra of MF after completing the microwave heating series show that the plastic was not fully cured, as evidenced by the absence of methylene linkages. The majority of migrants obtained from OM tests consisted of low molecular weight methylol melamine derivatives. The results indicate that microwave heating allowed demethylolation, addition and condensation reactions to occur, which was not the case when using conventional heating. This study demonstrates that microwave heating for 1-2 min in a repeated manner is of high concern in terms of consumer health. It was found that the service terms of melamine ware under microwave heating were drastically reduced, by more than 10-fold, as compared with the service terms under conventional heating. Hence, it is strongly recommended that manufacturers of MF articles provide instructions for use, e.g. "Do not use in microwave", which should be clearly visible to consumers and not easily detachable.

  7. Low-power near-field microwave applicator for localized heating of soft matter

    NASA Astrophysics Data System (ADS)

    Copty, A.; Sakran, F.; Golosovsky, M.; Davidov, D.; Frenkel, A.

    2004-06-01

    We report a 9 GHz near-field microwave probe for local surface heating of microwave absorbing materials. The probe radiates microwave energy through a narrow slot microfabricated at the apex of the dielectric resonator. The microwave energy is concentrated in a small region close to the applicator, in such a way that the microwave intensity there is very high. A temperature of 60-120 °C can be achieved in a spot size as small as 0.3×0.5 mm2, using an input power of only a few watts. The applicator can be used for local heating, coagulation, and melting of various soft-matter mediums. Particularly, we emphasize results on local heating and coagulation of egg-white and albumin which may be used as a "biological solder" for tissue welding applications.

  8. Phase Transformation of VO2 Nanoparticles Assisted by Microwave Heating

    PubMed Central

    Sikong, Lek.

    2014-01-01

    The microwave assisted synthesis nowadays attracts a great deal of attention. Monoclinic phase VO2 (M) was prepared from NH4VO3 and H2C2O4 · 2H2O by a rapid microwave assisted technique. The synthesis parameters, microwave irradiation time, microwave power, and calcinations temperature were systematically varied and their influences on the structure and morphology were evaluated. The microwave power level has been carried out in range 180–600 W. TEM analysis demonstrated nanosized samples. The structural and morphological properties were measured using XRD, TEM, and thermal analyses. The variations of vanadium phase led to thermochromic properties. PMID:24688438

  9. Improvement of heating uniformity in packaged acidified vegetables pasteurized with a 915 MHz continuous microwave system

    USDA-ARS?s Scientific Manuscript database

    Continuous microwave processing to produce shelf-stable acidified vegetables with moderate to high salt contents poses challenges in pasteurization due to reduced microwave penetration depths and non-uniform heating. Cups of sweetpotato, red bell pepper, and broccoli acidified to pH 3.8 with citric...

  10. A Comparison of Direct Heating During Radiofrequency and Microwave Ablation in Ex Vivo Liver

    SciTech Connect

    Andreano, Anita; Brace, Christopher L.

    2013-04-15

    This study was designed to determine the magnitude and spatial distribution of temperature elevations when using 480 kHz RF and 2.45 GHz microwave energy in ex vivo liver models. A total of 60 heating cycles (20 s at 90 W) were performed in normal, RF-ablated, and microwave-ablated liver tissues (n = 10 RF and n = 10 microwave in each tissue type). Heating cycles were performed using a 480-kHz generator and 3-cm cooled-tip electrode (RF) or a 2.45-GHz generator and 14-gauge monopole (microwave) and were designed to isolate direct heating from each energy type. Tissue temperatures were measured by using fiberoptic thermosensors 5, 10, and 15 mm radially from the ablation applicator at the depth of maximal heating. Power delivered, sensor location, heating rates, and maximal temperatures were compared using mixed effects regression models. No significant differences were noted in mean power delivered or thermosensor locations between RF and microwave heating groups (P > 0.05). Microwaves produced significantly more rapid heating than RF at 5, 10, and 15 mm in normal tissue (3.0 vs. 0.73, 0.85 vs. 0.21, and 0.17 vs. 0.09 Degree-Sign C/s; P < 0.05); and at 5 and 10 mm in ablated tissues (2.3 {+-} 1.4 vs. 0.7 {+-} 0.3, 0.5 {+-} 0.3 vs. 0.2 {+-} 0 Degree-Sign C/s, P < 0.05). The radial depth of heating was {approx}5 mm greater for microwaves than RF. Direct heating obtained with 2.45-GHz microwave energy using a single needle-like applicator is faster and covers a larger volume of tissue than 480-kHz RF energy.

  11. A finite element method based microwave heat transfer modeling of frozen multi-component foods

    NASA Astrophysics Data System (ADS)

    Pitchai, Krishnamoorthy

    Microwave heating is fast and convenient, but is highly non-uniform. Non-uniform heating in microwave cooking affects not only food quality but also food safety. Most food industries develop microwavable food products based on "cook-and-look" approach. This approach is time-consuming, labor intensive and expensive and may not result in optimal food product design that assures food safety and quality. Design of microwavable food can be realized through a simulation model which describes the physical mechanisms of microwave heating in mathematical expressions. The objective of this study was to develop a microwave heat transfer model to predict spatial and temporal profiles of various heterogeneous foods such as multi-component meal (chicken nuggets and mashed potato), multi-component and multi-layered meal (lasagna), and multi-layered food with active packages (pizza) during microwave heating. A microwave heat transfer model was developed by solving electromagnetic and heat transfer equations using finite element method in commercially available COMSOL Multiphysics v4.4 software. The microwave heat transfer model included detailed geometry of the cavity, phase change, and rotation of the food on the turntable. The predicted spatial surface temperature patterns and temporal profiles were validated against the experimental temperature profiles obtained using a thermal imaging camera and fiber-optic sensors. The predicted spatial surface temperature profile of different multi-component foods was in good agreement with the corresponding experimental profiles in terms of hot and cold spot patterns. The root mean square error values of temporal profiles ranged from 5.8 °C to 26.2 °C in chicken nuggets as compared 4.3 °C to 4.7 °C in mashed potatoes. In frozen lasagna, root mean square error values at six locations ranged from 6.6 °C to 20.0 °C for 6 min of heating. A microwave heat transfer model was developed to include susceptor assisted microwave heating of a

  12. Comparative decomposition kinetics of neutral monosaccharides by microwave and induction heating treatments.

    PubMed

    Tsubaki, Shuntaro; Oono, Kiriyo; Onda, Ayumu; Yanagisawa, Kazumichi; Azuma, Jun-ichi

    2013-06-28

    The stabilities of five neutral monosaccharides (glucose, galactose, mannose, arabinose, and xylose) were kinetically compared after the molecules were submitted to microwave heating (internal heating) and induction heating (external heating) under completely identical thermal histories by employing PID (proportional, integral, and derivative) temperature controlled ovens and homogeneous mixing. By heating in water at 200°C, the rate constants for the decomposition reactions varied from 2.13×10(-4) to 3.87×10(-4)s(-1) for microwave heating; however, the values increased by 1.1- to 1.5-fold for induction heating. Similarly, in a dilute (0.8%) sulfuric acid solution, the decomposition rate constants varied from 0.61×10(-3) to 2.00×10(-3)s(-1) for microwave heating; however, the values increased by 1.5- to 2.2-fold for induction heating. The results show that microwave heating imparts greater stability to neutral monosaccharides than does induction heating. The undesirable decomposition of monosaccharides at the surface boundary of reactor walls may have increased the probability of monosaccharide decomposition during induction heating.

  13. Specific features of waveguide heating due to transmission of high-power microwave signals

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, I. V.; Gotselyuk, O. B.; Novikov, E. S.; Demin, V. G.

    2017-01-01

    Waveguide heating due to transmission of microwave signals is studied. Mathematical models are developed to evaluate heat liberation, and differential equations of thermal balance are derived with allowance for different working conditions of waveguides. The results prove the necessity of the further study of the effect of heat liberation in waveguides on strength and functional characteristics.

  14. Optimization and stabilization of gold nanoparticles by using herbal plant extract with microwave heating.

    PubMed

    Yasmin, Akbar; Ramesh, Kumaraswamy; Rajeshkumar, Shanmugam

    2014-01-01

    In this study, we have synthesized the gold nanoparticles by using Hibiscus rosa-sinensis, a medicinal plant. The gold nanoparticles were synthesized rapidly by the involvement of microwave heating. By changing of plant extract concentration, gold solution concentration, microwave heating time and power of microwave heating the optimized condition was identified. The surface Plasmon resonance found at 520 nm confirmed the gold nanoparticles synthesis. The spherical sized nanoparticles in the size range of 16-30 nm were confirmed by Transmission Electron Microscope (TEM). The stability of the nanoparticles is very well proved in the invitro stability tests. The biochemical like alkaloids and flavonoids play a vital role in the nanoparticles synthesis was identified using the Fourier Transform Infrared Spectroscopy (FTIR). Combining the phytochemical and microwave heating, the rapid synthesis of gold nanoparticles is the novel process for the medically applicable gold nanoparticles production.

  15. Furfural Synthesis from d-Xylose in the Presence of Sodium Chloride: Microwave versus Conventional Heating.

    PubMed

    Xiouras, Christos; Radacsi, Norbert; Sturm, Guido; Stefanidis, Georgios D

    2016-08-23

    We investigate the existence of specific/nonthermal microwave effects for the dehydration reaction of xylose to furfural in the presence of NaCl. Such effects are reported for sugars dehydration reactions in several literature reports. To this end, we adopted three approaches that compare microwave-assisted experiments with a) conventional heating experiments from the literature; b) simulated conventional heating experiments using microwave-irradiated silicon carbide (SiC) vials; and at c) different power levels but the same temperature by using forced cooling. No significant differences in the reaction kinetics are observed using any of these methods. However, microwave heating still proves advantageous as it requires 30 % less forward power compared to conventional heating (SiC vial) to achieve the same furfural yield at a laboratory scale. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Optimization and stabilization of gold nanoparticles by using herbal plant extract with microwave heating

    NASA Astrophysics Data System (ADS)

    Yasmin, Akbar; Ramesh, Kumaraswamy; Rajeshkumar, Shanmugam

    2014-04-01

    In this study, we have synthesized the gold nanoparticles by using Hibiscus rosa-sinensis, a medicinal plant. The gold nanoparticles were synthesized rapidly by the involvement of microwave heating. By changing of plant extract concentration, gold solution concentration, microwave heating time and power of microwave heating the optimized condition was identified. The surface Plasmon resonance found at 520 nm confirmed the gold nanoparticles synthesis. The spherical sized nanoparticles in the size range of 16-30 nm were confirmed by Transmission Electron Microscope (TEM). The stability of the nanoparticles is very well proved in the invitro stability tests. The biochemical like alkaloids and flavonoids play a vital role in the nanoparticles synthesis was identified using the Fourier Transform Infrared Spectroscopy (FTIR). Combining the phytochemical and microwave heating, the rapid synthesis of gold nanoparticles is the novel process for the medically applicable gold nanoparticles production.

  17. Microwave frequency material properties of PBS 9501 and PBX 9501 and small scale heating experiments

    NASA Astrophysics Data System (ADS)

    Glover, B. B.; Daily, M. E.; Son, S. F.; Groven, L. J.

    2014-05-01

    This work reports the microwave frequency dielectric properties of PBX 9501 and one of its representative mocks, PBS 9501, within 1-20 GHz. From these measurements it is shown that the binder system has a strong influence on microwave heating of such compositions resulting in significant temperature gradients within the individual HMX or sugar crystals at high microwave heating rates. Using the measured dielectric properties, COMSOL 4.3 Multiphysics was used to simulate and optimize a microwave applicator with a high electric field to input power ratio. The simulated applicator design indicated subsecond heating to decomposition for PBX 9501 and was validated with small scale experiments on both PBS 9501 and PBX 9501. At approximately 2.45 GHz and 100 W applied power, PBS 9501 decomposition was observed shortly (< 34 ms) after a measured surface temperature of 70 °C (binder system melts). Finally, rapid heating of PBX 9501 was also shown in the optimized cavity.

  18. Microwave Ovens

    MedlinePlus

    ... Standards Industry Guidance Other Resources Description Microwave ovens heat food using microwaves, a form of electromagnetic radiation ... vibration results in friction between molecules, which produces heat that cooks the food. Risks/Benefits Microwaves are ...

  19. Preparation of Ti-coated diamond particles by microwave heating

    NASA Astrophysics Data System (ADS)

    Gu, Quanchao; Peng, Jinghui; Xu, Lei; Srinivasakannan, C.; Zhang, Libo; Xia, Yi; Wu, Qingtian; Xia, Hongying

    2016-12-01

    Depositing strong carbide-forming elements on diamond surface can dramatically improve the interfacial bonding strength between diamond grits and metal matrix. In the present work, investigation on the preparation of Ti-coated diamond particles by microwave heating has been conducted. The morphology, microstructure, and the chemical composition of Ti-coated diamond particles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive x-ray spectrometer (EDX). The thickness of Ti coating was measured and the interfacial binding strength between Ti coating and diamond was analyzed. The results show that the surface of the diamond particles could be successfully coated with Ti, forming a uniform and continuous Ti-coated layer. The TiC was found to form between the surface of diamond particles and Ti-coated layer. The amount of TiC as well as the thickness of coating increased with increasing coating temperature, furthermore, the grain size of the coating also grew gradually. The interfacial bonding strength between coating and diamond was found to be best at the temperature of 760 °C.

  20. Multiple tube structure for heating uniformity and efficiency optimization of microwave ovens

    NASA Astrophysics Data System (ADS)

    Zhou, Rong; Yang, Xiaoqing; Sun, Di; Jia, Guozhu

    2015-02-01

    Microwave heating is widely applied to microwave assisted chemical reactions in modified domestic microwave ovens, however, the potential issues (non-uniformity and low heating efficiency) still exist during the heating process. In this paper, a new heating model of multiple tube structure is proposed and the relevant simulations and experiments of heating water were performed based on the computational platform COMSOL Multi-physics software in order to achieve the better temperature uniformity and heating efficiency. Besides, the influence of the instability of microwave ovens on the heating performances of the optimal heating models was analyzed. The simulation results show that the heating uniformity and efficiency of water in optimal six tube structure increased by 7.1% and 68.5% (30 mL), 9.2% and 61% (60 mL) respectively compared with the optimal single tube structure. Moreover, the heating performances of the optimal heating models do not change obviously, while the working frequency and power change slightly. The simulation results are in good agreement with the experiment data.

  1. Apparatus for the joining of ceramics using microwave hybrid heating

    SciTech Connect

    Cozzi, A.D.; Ferber, M.K.; Tennery, V.J.

    1995-12-31

    An apparatus was designed and constructed to facilitate the joining of ceramics in a microwave field. The microwave unit used is a modified Goldstar MA-1172M household microwave oven. The maximum load that can be applied is 2.24 kN. Temperature can be monitored with either a shielded type R thermocouple or an optical pyrometer. Measurements of the temperature and applied load are collected remotely.

  2. Ultraviolet spectrophotometric evaluation of corn oil oxidative stability during microwave heating and oven test.

    PubMed

    Vieira, T M; Regitano-D'Arce, M A

    1999-06-01

    The effect of microwave heating on the oxidative stability of corn oil was determined by absorptivity in the UV spectrum and by peroxide and acid values. Oil samples with antioxidants BHA/BHT (1:1; 200 mg kg(-)(1)), with and without citric acid, were heated in a microwave oven (800 W, 2450 MHz) for 0-36 min. Absorptivity at 232 and 270 nm increased during microwave exposure. Control values of absorptivity at 232 nm increased from 3.568 to 12.874 after 36 min of heating. Peroxide value showed a significant difference in the initial stage of heating (0-6 min), but after this time, the peroxide value decreased due to the instability of hydroperoxides at high temperatures. Control 232 nm absorptivities after 6 days in the oven test were similar to those after 32-36 min of microwave heating. Effective antioxidants in the oven test did not show any protection during microwave heating. UV spectrophotometry is a suitable tool for microwave oxidation monitoring.

  3. Frequency Distribution in Domestic Microwave Ovens and Its Influence on Heating Pattern.

    PubMed

    Luan, Donglei; Wang, Yifen; Tang, Juming; Jain, Deepali

    2017-02-01

    In this study, snapshots of operating frequency profiles of domestic microwave ovens were collected to reveal the extent of microwave frequency variations under different operation conditions. A computer simulation model was developed based on the finite difference time domain method to analyze the influence of the shifting frequency on heating patterns of foods in a microwave oven. The results showed that the operating frequencies of empty and loaded domestic microwave ovens varied widely even among ovens of the same model purchased on the same date. Each microwave oven had its unique characteristic operating frequencies, which were also affected by the location and shape of the load. The simulated heating patterns of a gellan gel model food when heated on a rotary plate agreed well with the experimental results, which supported the reliability of the developed simulation model. Simulation indicated that the heating patterns of a stationary model food load changed with the varying operating frequency. However, the heating pattern of a rotary model food load was not sensitive to microwave frequencies due to the severe edge heating overshadowing the effects of the frequency variations. © 2016 Institute of Food Technologists®.

  4. Effect of microwave heating on the quality characteristics of canola oil in presence of palm olein.

    PubMed

    Ali, M Abbas; Nouruddeen, Zahrau Bamalli; Muhamad, Ida Idayu; Latip, Razam Abd; Othman, Noor Hidayu

    2013-01-01

    Microwave heating is one of the most attractive cooking methods for food preparation, commonly employed in households and especially in restaurants for its high speed and convenience. The chemical constituents of oils that degrade during microwave heating do so at rates that vary with heating temperature and time in a similar manner to other type of processing methods. The rate of quality characteristics of the oil depends on the fatty acid composition and the minor components during heating. Addition of oxidative-stable palm olein (PO) to heat sensitive canola oil (CO), may affect the quality characteristics of CO during microwave heating. The aim of this study was to evaluate how heat treatments by microwave oven affect the quality of CO in presence of PO. The blend was prepared in the volume ratio of 40:60 (PO:CO, PC). Microwave heating test was performed for different periods (2, 4, 8, 12, 16 and 20 min) at medium power setting for the samples of CO and PC. The changes in quality characteristics of the samples during heating were determined by analytical and instrumental methods. In this study, refractive index, free fatty acid content, peroxide value, p-anisidine value, TOTOX value, specific extinction, viscosity, polymer content, polar compounds and food oil sensor value of the oils all increased, whereas iodine value and C₁₈.₂ /C₁₆:₀ ratio decreased as microwave heating progressed. Based on the most oxidative stability criteria, PO addition led to a slower deterioration of CO at heating temperatures. The effect of microwave heating on the fatty acid composition of the samples was not remarkable. PO addition decelerated the formation of primary and secondary oxidation products in CO. However, effect of adding PO to CO on the formation of free fatty acids and polymers during microwave treatment was not significant (P < 0.05). No significant difference in food oil sensor value was detected between CO and PC throughout the heating periods. Microwave

  5. Electromagnetic simulations of microwave heating experiments using reaction vessels made out of silicon carbide.

    PubMed

    Robinson, John; Kingman, Sam; Irvine, Derek; Licence, Peter; Smith, Alastair; Dimitrakis, Georgios; Obermayer, David; Kappe, C Oliver

    2010-09-28

    There is a growing body of literature which reports the use of silicon carbide vessels to shield reaction mixtures during microwave heating. In this paper we use electromagnetic simulations and microwave experiments to show that silicon carbide vessels do not exclude the electric field, and that dielectric heating of reaction mixtures will take place in addition to heat transfer from the silicon carbide. The contribution of dielectric heating and heat transfer depends on the dielectric properties of the mixture, and the temperature at which the reaction is carried out. Solvents which remain microwave absorbent at high temperatures, such as ionic liquids, will heat under the direct influence of the electric field from 30-250 degrees C. Solvents which are less microwave absorbent at higher temperatures will be heated by heat-transfer only at temperatures in excess of 150 degrees C. The results presented in this paper suggest that the influence of the electric field cannot be neglected when interpreting microwave assisted synthesis experiments in silicon carbide vessels.

  6. Parallel microwave chemistry in silicon carbide reactor platforms: an in-depth investigation into heating characteristics.

    PubMed

    Damm, Markus; Kappe, C Oliver

    2009-11-01

    The heating behavior of silicon carbide reaction platforms under 2.45 GHz microwave irradiation was investigated with the aid of online thermoimaging cameras and multiple-channel fiber-optic probe temperature sensors placed inside the wells/vials of the silicon carbide microtiter plates. Microwave irradiation leads to a rapid and homogeneous heating of the entire plate, with minimal deviations in the temperature recorded at different positions of the plate or inside the wells. In temperature-controlled experiments using dedicated multimode reactors, solvents with different microwave absorption characteristics can be heated in parallel in individual wells/vials of the silicon carbide plate reaching the same set temperature. Due to the large heat capacity and high thermal conductivity of silicon carbide, the plates are able to moderate any field inhomogeneities inside a microwave cavity. Although the heating of the plates can be performed extremely efficiently inside a microwave reactor, heating and synthetic applications can alternatively be carried out by applying conventional conductive heating of the silicon carbide plates on a standard hotplate. Due to the slower heating of the silicon carbide material under these conditions, somewhat longer reaction times will be required.

  7. A microwave-heated infrared reaction cell for the in situ study of heterogeneous catalysts.

    PubMed

    Silverwood, Ian P; McDougall, Gordon S; Gavin Whittaker, A

    2006-12-14

    A transmission infrared microreactor cell which holds a pressed disc in a controlled atmosphere and allows microwave and conventional heating up to 423 K is demonstrated using the oxidation of carbon monoxide over the standard catalyst EUROPT-1. Optical characteristics are determined by the choice of CaF2 as the window material, allowing transmission from 77,000-1000 cm(-1). An oscillating microwave power regime with a peak height of 200 W is used and time-resolved infrared spectra and mass spectrometry show oscillations in the reaction which correspond to the microwave heating.

  8. [Dependence of microwave produced heating of cell suspensions on their concentration].

    PubMed

    Dergacheva, I P; Morozov, I I; Petin, B G

    1998-01-01

    The kinetics of microwave (7 GHz) heating of yeast and bacterial cell suspensions of different concentrations was investigated in the conditions of various thermoisolation of irradiated samples. It was established that independently of type of microorganisms, microwaves produced a more intensive heating of cell suspension in comparison with suspension fluid. The degree of heating was shown to increase with cell concentration. This effect was more expressed under conditions of thermoisolation. At the same irradiation doses and cell concentrations the yeast suspension was heated more vigorously than bacterial one. These differences disappeared when the rise in sample temperature was related to the total cell volume.

  9. Simple method for highlighting the temperature distribution into a liquid sample heated by microwave power field

    SciTech Connect

    Surducan, V.; Surducan, E.; Dadarlat, D.

    2013-11-13

    Microwave induced heating is widely used in medical treatments, scientific and industrial applications. The temperature field inside a microwave heated sample is often inhomogenous, therefore multiple temperature sensors are required for an accurate result. Nowadays, non-contact (Infra Red thermography or microwave radiometry) or direct contact temperature measurement methods (expensive and sophisticated fiber optic temperature sensors transparent to microwave radiation) are mainly used. IR thermography gives only the surface temperature and can not be used for measuring temperature distributions in cross sections of a sample. In this paper we present a very simple experimental method for temperature distribution highlighting inside a cross section of a liquid sample, heated by a microwave radiation through a coaxial applicator. The method proposed is able to offer qualitative information about the heating distribution, using a temperature sensitive liquid crystal sheet. Inhomogeneities as smaller as 1°-2°C produced by the symmetry irregularities of the microwave applicator can be easily detected by visual inspection or by computer assisted color to temperature conversion. Therefore, the microwave applicator is tuned and verified with described method until the temperature inhomogeneities are solved.

  10. Microwave Heating of TV-Dinner Type Products

    USDA-ARS?s Scientific Manuscript database

    Modified from an inverter-based microwave oven, a new microwave system was developed to pasteurize mechanically tenderized beef, inoculated with Escherichia coli O157:H7 and placed into a 12 oz CPET tray containing de-ionized water. The system allowed the sample surface temperature to first increas...

  11. An optical fiber sensing technique for temperature distribution measurements in microwave heating

    NASA Astrophysics Data System (ADS)

    Wada, Daichi; Sugiyama, Jun-ichi; Zushi, Hiroaki; Murayama, Hideaki

    2015-08-01

    We introduce an optical fiber sensing technique that can measure the temperature distributions along a fiber during microwave heating. We used a long-length fiber Bragg grating (FBG) as an electromagnetic-immune sensor and interrogated temperature distributions along the FBG by an optical frequency domain reflectometry. Water in a glass tube with a length of 820 mm was heated in a microwave oven, and its temperature distribution along the glass tube was measured using the sensing system. The temperature distribution was obtained in 5 mm intervals. Infrared radiometry was also used to compare the temperature measurement results. Time and spatial variations of the temperature distribution profiles were monitored for several microwave input powers. The results clearly depict inhomogeneous temperature profiles. The applicability and effectiveness of the optical fiber distributed measurement technique in microwave heating are demonstrated.

  12. The microwave heating mechanism of N-(4-methoxybenzyliden)-4-butylaniline in liquid crystalline and isotropic phases as determined using in situ microwave irradiation NMR spectroscopy.

    PubMed

    Tasei, Yugo; Tanigawa, Fumikazu; Kawamura, Izuru; Fujito, Teruaki; Sato, Motoyasu; Naito, Akira

    2015-04-14

    Microwave heating effects are widely used in the acceleration of organic, polymerization and enzymatic reactions. These effects are primarily caused by the local heating induced by microwave irradiation. However, the detailed molecular mechanisms associated with microwave heating effects on the chemical reactions are not yet well understood. This study investigated the microwave heating effect of N-(4-methoxybenzylidene)-4-butylaniline (MBBA) in liquid crystalline and isotropic phases using in situ microwave irradiation nuclear magnetic resonance (NMR) spectroscopy, by obtaining (1)H NMR spectra of MBBA under microwave irradiation. When heated simply using the temperature control unit of the NMR instrument, the liquid crystalline MBBA was converted to the isotropic phase exactly at its phase transition temperature (Tc) of 41 °C. The application of microwave irradiation at 130 W for 90 s while maintaining the instrument temperature at 20 °C generated a small amount of isotropic phase within the bulk liquid crystal. The sample temperature of the liquid crystalline state obtained during microwave irradiation was estimated to be 35 °C by assessing the linewidths of the (1)H NMR spectrum. This partial transition to the isotropic phase can be attributed to a non-equilibrium local heating state induced by the microwave irradiation. The application of microwave at 195 W for 5 min to isotropic MBBA while maintaining an instrument temperature of 50 °C raised the sample temperature to 160 °C. In this study, the MBBA temperature during microwave irradiation was estimated by measuring the temperature dependent chemical shifts of individual protons in the sample, and the different protons were found to indicate significantly different temperatures in the molecule. These results suggest that microwave heating polarizes bonds in polar functional groups, and this effect may partly explain the attendant acceleration of organic reactions.

  13. Silver halide fiber optic radiometry for temperature monitoring and control of tissues heated by microwave

    NASA Astrophysics Data System (ADS)

    Shenfeld, Ofer; Belotserkovsky, Edward; Goldwasser, Benad; Zur, Albert; Katzir, Abraham

    1993-02-01

    The heating of tissue by microwave radiation has attained a place of importance in various medical fields, such as the treatment of malignancies, urinary retention, and hypothermia. Accurate temperature measurements in these treated tissues is important for treatment planning and for the control of the heating process. It is also important to be able to measure spacial temperature distribution in the tissues because they are heated in a nonuniform way by the microwave radiation. Conventional temperature sensors used today are inaccurate in the presence of microwave radiation and require contact with the heated tissue. Fiber optic radiometry makes it possible to measure temperatures accurately in the presence of microwave radiation and does not require contact with the tissue. Accurate temperature measurements of tissues heated by microwave was obtained using a silver halide optic radiometer, enabling control of the heating process in other regions of the tissue samples. Temperature mappings of the heated tissues were performed and the nonuniform temperature distributions in these tissues was demonstrated.

  14. De-crystallization of Uric Acid Crystals in Synovial Fluid Using Gold Colloids and Microwave Heating.

    PubMed

    Kioko, Bridgit; Ogundolie, Taiwo; Adebiyi, Morenike; Ettinoffe, Yehnara; Rhodes, Caleb; Gordon, Brittney; Thompson, Nishone; Mohammed, Muzaffer; Abel, Biebele; Aslan, Kadir

    In this study, we demonstrated a unique application of our Metal-Assisted and Microwave-Accelerated Evaporative Crystallization (MA-MAEC) technique for the de-crystallization of uric acid crystals, which causes gout in humans when monosodium urate crystals accumulate in the synovial fluid found in the joints of bones. Given the shortcomings of the existing treatments for gout, we investigated whether the MA-MAEC technique can offer an alternative solution to the treatment of gout. Our technique is based on the use of metal nanoparticles (i.e., gold colloids) with low microwave heating to accelerate the de-crystallization process. In this regard, we employed a two-step process; (i) crystallization of uric acid on glass slides, which act as a solid platform to mimic a bone, (ii) de-crystallization of uric acid crystals on glass slides with the addition of gold colloids and low power microwave heating, which act as "nano-bullets" when microwave heated in a solution. We observed that the size and number of the uric acid crystals were reduced by >60% within 10 minutes of low power microwave heating. In addition, the use of gold colloids without microwave heating (i.e. control experiment) did not result in the de-crystallization of the uric acid crystals, which proves the utility of our MA-MAEC technique in the de-crystallization of uric acid.

  15. Microwave heating device for internal heating convection experiments, applied to Earth's mantle dynamics.

    PubMed

    Surducan, E; Surducan, V; Limare, A; Neamtu, C; Di Giuseppe, E

    2014-12-01

    We report the design, construction, and performances of a microwave (MW) heating device for laboratory experiments with non-contact, homogeneous internal heating. The device generates MW radiation at 2.47 GHz from a commercial magnetron supplied by a pulsed current inverter using proprietary, feedback based command and control hardware and software. Specially designed MW launchers direct the MW radiation into the sample through a MW homogenizer, devised to even the MW power distribution into the sample's volume. An adjustable MW circuit adapts the MW generator to the load (i.e., the sample) placed in the experiment chamber. Dedicated heatsinks maintain the MW circuits at constant temperature throughout the experiment. Openings for laser scanning for image acquisition with a CCD camera and for the cooling circuits are protected by special MW filters. The performances of the device are analyzed in terms of heating uniformity, long term output power stability, and load matching. The device is used for small scale experiments simulating Earth's mantle convection. The 30 × 30 × 5 cm(3) convection tank is filled with a water‑based viscous fluid. A uniform and constant temperature is maintained at the upper boundary by an aluminum heat exchanger and adiabatic conditions apply at the tank base. We characterize the geometry of the convective regime as well as its bulk thermal evolution by measuring the velocity field by Particle Image Velocimetry and the temperature field by using Thermochromic Liquid Crystals.

  16. Microwave heating device for internal heating convection experiments, applied to Earth's mantle dynamics

    SciTech Connect

    Surducan, E.; Surducan, V.; Neamtu, C.; Limare, A.; Di Giuseppe, E.

    2014-12-15

    We report the design, construction, and performances of a microwave (MW) heating device for laboratory experiments with non-contact, homogeneous internal heating. The device generates MW radiation at 2.47 GHz from a commercial magnetron supplied by a pulsed current inverter using proprietary, feedback based command and control hardware and software. Specially designed MW launchers direct the MW radiation into the sample through a MW homogenizer, devised to even the MW power distribution into the sample's volume. An adjustable MW circuit adapts the MW generator to the load (i.e., the sample) placed in the experiment chamber. Dedicated heatsinks maintain the MW circuits at constant temperature throughout the experiment. Openings for laser scanning for image acquisition with a CCD camera and for the cooling circuits are protected by special MW filters. The performances of the device are analyzed in terms of heating uniformity, long term output power stability, and load matching. The device is used for small scale experiments simulating Earth's mantle convection. The 30 × 30 × 5 cm{sup 3} convection tank is filled with a water‑based viscous fluid. A uniform and constant temperature is maintained at the upper boundary by an aluminum heat exchanger and adiabatic conditions apply at the tank base. We characterize the geometry of the convective regime as well as its bulk thermal evolution by measuring the velocity field by Particle Image Velocimetry and the temperature field by using Thermochromic Liquid Crystals.

  17. Microwave heating device for internal heating convection experiments, applied to Earth's mantle dynamics

    NASA Astrophysics Data System (ADS)

    Surducan, E.; Surducan, V.; Limare, A.; Neamtu, C.; Di Giuseppe, E.

    2014-12-01

    We report the design, construction, and performances of a microwave (MW) heating device for laboratory experiments with non-contact, homogeneous internal heating. The device generates MW radiation at 2.47 GHz from a commercial magnetron supplied by a pulsed current inverter using proprietary, feedback based command and control hardware and software. Specially designed MW launchers direct the MW radiation into the sample through a MW homogenizer, devised to even the MW power distribution into the sample's volume. An adjustable MW circuit adapts the MW generator to the load (i.e., the sample) placed in the experiment chamber. Dedicated heatsinks maintain the MW circuits at constant temperature throughout the experiment. Openings for laser scanning for image acquisition with a CCD camera and for the cooling circuits are protected by special MW filters. The performances of the device are analyzed in terms of heating uniformity, long term output power stability, and load matching. The device is used for small scale experiments simulating Earth's mantle convection. The 30 × 30 × 5 cm3 convection tank is filled with a water-based viscous fluid. A uniform and constant temperature is maintained at the upper boundary by an aluminum heat exchanger and adiabatic conditions apply at the tank base. We characterize the geometry of the convective regime as well as its bulk thermal evolution by measuring the velocity field by Particle Image Velocimetry and the temperature field by using Thermochromic Liquid Crystals.

  18. Low-power microwave-mediated heating for microchip-based PCR.

    PubMed

    Marchiarullo, Daniel J; Sklavounos, Angelique H; Oh, Kyudam; Poe, Brian L; Barker, N Scott; Landers, James P

    2013-09-07

    Microwave energy has been used to rapidly heat food and drinks for decades, in addition to assisting other chemical reactions. However, only recently has microwave energy been applied in microfluidic systems to heat solution in reaction chambers, in particular, the polymerase chain reaction (PCR). One of the difficulties in developing microwave-mediated heating on a microchip is the construction of the appropriate architecture for delivery of the energy to specific micro-areas on the microchip. This work employs commercially-available microwave components commonly used in the wireless communications industry to generate a microwave signal, and a microstrip transmission line to deliver the energy to a 1 μL reaction chamber fabricated in plastic microdevices. A model was developed to create transmission lines that would optimally transmit energy to the reaction chamber at a given frequency, minimizing energy usage while focusing microwave delivery to the target chamber. Two different temperature control methods were demonstrated, varying microwave power or frequency. This system was used to amplify a fragment of the lambda-phage genome, thereby demonstrating its potential for integration into a portable PCR system.

  19. Behavioral and autonomic thermoregulation in hamsters during microwave-induced heat exposure

    SciTech Connect

    Gordon, C.J.; Long, M.D.; Fehlner, K.S.

    1984-01-01

    Preferred ambient temperature (Ta) and ventilatory frequency were measured in free-moving hamsters exposed to 2450-MHz microwaves. A waveguide exposure system that permits continuous monitoring of the absorbed heat load accrued from microwave exposure was imposed with a longitudinal temperature gradient which allowed hamsters to select their preferred Ta. Ventilatory frequency was monitored remotely by analysing the rhythmic shifts in unabsorbed microwave energy passing down the waveguide. Without microwave exposure hamsters selected an average T2 of 30.2 C. This preferred Ta did not change until the rate of heat absorption (SAR) from microwave exposure exceeded approx. 2 W kg-1. In a separate experiment, a SAR of 2.0 W kg-1 at a Ta of 30C was shown to promote an average 0.5 C increase in colonic temperature. Hamsters maintained their ventilatory frequency at baseline levels by selecting a cooler Ta during microwave exposure. These data support previous studies suggesting that during thermal stress behavioral thermo-regulation (i.e. preferred Ta) takes prescedence over autonomic thermoregulation (i.e. ventilatory frequency). It is apparent that selecting a cooler Ta is a more efficient and/or effective than autonomic thermoregulation for dissipating a heat load accrued from microwave exposure.

  20. Microwave heating of water, ice, and saline solution: molecular dynamics study.

    PubMed

    Tanaka, Motohiko; Sato, Motoyasu

    2007-01-21

    In order to study the heating process of water by the microwaves of 2.5-20 GHz frequencies, the authors have performed molecular dynamics simulations by adopting a nonpolarizable water model that has fixed point charges on a rigid-body geometry. All runs are started from the equilibrated states derived from the I(c) ice with given density and temperature. In the presence of microwaves, the molecules of liquid water exhibit rotational motion whose average phase is delayed from the microwave electric field. Microwave energy is transferred to the kinetic and intermolecular energies of water, where one-third of the absorbed microwave energy is stored as the latter energy. The water in ice phase is scarcely heated by microwaves because of the tight hydrogen-bonded network of water molecules. Dilute salt water is significantly more heated than pure water because of the field-induced motion of salt ions, especially that of large-size ions, by the microwave electric field and energy transfer to water molecules by collisions.

  1. Effect of chlorine, blanching, freezing, and microwave heating on Cryptosporidium parvum viability inoculated on green peppers.

    PubMed

    Duhain, G L M C; Minnaar, A; Buys, E M

    2012-05-01

    Cryptosporidium parvum oocysts have been found on the surface of vegetables in both developed and developing countries. C. parvum can contaminate vegetables via various routes, including irrigation water. This study investigated the effect of individual treatments of chlorine, blanching, blast freezing, and microwave heating, as well as combined treatments of chlorine and freezing, and chlorine and microwave heating on the viability of C. parvum oocysts inoculated on green peppers. The viability of the oocysts after the treatments was assessed using propidium iodide and a flow cytometer. Based on the propidium iodide staining, the chlorine treatments did not affect the viability of the oocysts. Blast freezing significantly inactivated 20% of the oocysts. Microwave heating and blanching significantly inactivated 93% of oocysts. Treatment with chlorine followed by blast freezing did not affect the viability of the oocysts significantly. Treatment with chlorine and microwave heating was significantly more effective than microwave heating alone and inactivated 98% of the oocysts. The study indicates that C. parvum oocysts are sensitive to heat and, to some extent, to blast freezing, but are resistant to chlorine. Therefore, the use of chlorine during vegetable processing is not a critical control point for C. parvum oocysts, and the consumption of raw or minimally processed vegetables may constitute a health risk as C. parvum oocysts can still be found viable on ready-to-eat, minimally processed vegetables.

  2. Vesicouretal reflux in children: A phantom study of microwave heating and radiometric thermometry of pediatric bladder

    PubMed Central

    Birkelund, Yngve; Klemetsen, Øystein; Jacobsen, Svein K.; Arunachalam, Kavitha; Maccarini, Paolo; Stauffer, Paul R.

    2012-01-01

    We have investigated the use of microwave heating and radiometry to safely heat urine inside a pediatric bladder. The medical application for this research is to create a safe and reliable method to detect vesicoureteral reflux, a pediatric disorder, where urine flow is reversed and flows from the bladder back up into the kidney. Using fat and muscle tissue models, we have performed both experimental and numerical simulations of a pediatric bladder model using planar dual concentric conductor microstrip antennas at 915 MHz for microwave heating. A planar elliptical antenna connected to a 500 MHz bandwidth microwave radiometer centered at 3.5 GHz was used for non-invasive temperature measurement inside tissue. Temperatures were measured in the phantom models at points during the experiment with implanted fiberoptic sensors, and 2D distributions in cut planes at depth in the phantom with an infrared camera at the end of the experiment. Cycling between 20 second with 20 Watts power for heating, and 10 seconds without power to allow for undisturbed microwave radiometry measurements, the experimental results show that the target tissue temperature inside the phantom increases fast and that the radiometer provides useful measurements of spatially averaged temperature of the illuminated volume. The presented numerical and experimental results show excellent concordance, which confirms that the proposed system for microwave heating and radiometry is applicable for safe and reliable heating of pediatric bladder. PMID:21900069

  3. Nucleation and crystallization of tailing-based glass-ceramics by microwave heating

    NASA Astrophysics Data System (ADS)

    Li, Bao-wei; Li, Hong-xia; Zhang, Xue-feng; Jia, Xiao-lin; Sun, Zhi-chao

    2015-12-01

    The effect of microwave radiation on the nucleation and crystallization of tailing-based glass-ceramics was investigated using a 2.45 GHz multimode microwave cavity. Tailing-based glass samples were prepared from Shandong gold tailings and Guyang iron tailings utilizing a conventional glass melting technique. For comparison, the tailing-based glass samples were crystallized using two different heat-treatment methods: conventional heating and hybrid microwave heating. The nucleation and crystallization temperatures were determined by performing a differential thermal analysis of the quenched tailing-based glass. The prepared glass-ceramic samples were further characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, thermal expansion coefficient measurements, and scanning electron microscopy. The results demonstrated that hybrid microwave heating could be successfully used to crystallize the tailing-based glass, reduce the processing time, and decrease the crystallization temperature. Furthermore, the results indicated that the nucleation and crystallization mechanism of the hybrid microwave heating process slightly differs from that of the conventional heating process.

  4. Effect of Microwave Heating Conditions on the Preparation of High Surface Area Activated Carbon from Waste Bamboo

    NASA Astrophysics Data System (ADS)

    Wu, Jian; Hongying Xia; Zhang, Libo; Xia, Yi; Peng, Jinhui; Wang, Shixing; Zheng, Zhaoqiang; Zhang, Shengzhou

    2015-11-01

    The present study reports the effect of microwave power and microwave heating time on activated carbon adsorption ability. The waste bamboo was used to preparing high surface area activated carbon via microwave heating. The bamboo was carbonized for 2 h at 600°C to be used as the raw material. According to the results, microwave power and microwave heating time had a significant impact on the activating effect. The optimal KOH/C ratio of 4 was identified when microwave power and microwave heating time were 700 W and 15 min, respectively. Under the optimal conditions, surface area was estimated to be 3441 m2/g with pore volume of 2.093 ml/g and the significant proportion of activated carbon was microporous (62.3%). The results of Fourier transform infrared spectroscopy (FTIR) were illustrated that activated carbon surface had abundant functional groups. Additionally the pore structure is characterized using Scanning Electron Microscope (SEM).

  5. Effects of microwave heating on porous structure of regenerated powdered activated carbon used in xylose.

    PubMed

    Li, Wei; Wang, Xinying; Peng, Jinhui

    2014-01-01

    The regeneration of spent powdered activated carbons used in xylose decolourization by microwave heating was investigated. Effects of microwave power and microwave heating time on the adsorption capacity of regenerated activated carbons were evaluated. The optimum conditions obtained are as follows: microwave power 800W; microwave heating time 30min. Regenerated activated carbon in this work has high adsorption capacities for the amount of methylene blue of 16 cm3/0.1 g and the iodine number of 1000.06mg/g. The specific surface areas of fresh commercial activated carbon, spent carbon and regenerated activated carbon were calculated according to the Brunauer, Emmett and Teller method, and the pore-size distributions of these carbons were characterized by non-local density functional theory (NLDFT). The results show that the specific surface area and the total pore volume of regenerated activated carbon are 1064 m2/g and 1.181 mL/g, respectively, indicating the feasibility of regeneration of spent powdered activated carbon used in xylose decolourization by microwave heating. The results of surface fractal dimensions also confirm the results of isotherms and NLDFT.

  6. Microwave heating: Industrial applications. (Latest citations from the EI Compendex*plus database). Published Search

    SciTech Connect

    1996-04-01

    The bibliography contains citations concerning industrial uses and design of microwave heating equipment. Citations discuss applications in food processing, industrial heating, vulcanization, textile finishing, metallurgical sintering, ceramic manufacturing, paper industries, and curing of polymers. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  7. A Half Century of Research on Agricultural Applications for RF and Microwave Dielectric Heating

    USDA-ARS?s Scientific Manuscript database

    Basic principles of radio-frequency and microwave dielectric heating are presented, and research reports and reviews published over the past 50 or 60 years are identified for various dielectric heating applications that have been explored for potential use in the field of agriculture. Included are ...

  8. 21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Radiofrequency radiation for the heating of food... PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources § 179.30 Radiofrequency radiation for the heating of food, including microwave frequencies. Radiofrequency radiation, including...

  9. 21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Radiofrequency radiation for the heating of food... PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources § 179.30 Radiofrequency radiation for the heating of food, including microwave frequencies. Radiofrequency radiation, including...

  10. 21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Radiofrequency radiation for the heating of food... PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources § 179.30 Radiofrequency radiation for the heating of food, including microwave frequencies. Radiofrequency radiation, including...

  11. 21 CFR 179.30 - Radiofrequency radiation for the heating of food, including microwave frequencies.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Radiofrequency radiation for the heating of food... PRODUCTION, PROCESSING AND HANDLING OF FOOD Radiation and Radiation Sources § 179.30 Radiofrequency radiation for the heating of food, including microwave frequencies. Radiofrequency radiation, including...

  12. Synthesis of WC powder through microwave heating of WO3-C mixture

    NASA Astrophysics Data System (ADS)

    Behnami, Amir Karimzadeh; Hoseinpur, Arman; Sakaki, Masoud; Bafghi, Mohammad Sh.; Yanagisawa, Kazumichi

    2017-02-01

    A simple, easy, and low-cost process for the fabrication of tungsten carbide (WC) powder through microwave heating of WO3-C mixtures was developed. Thermodynamic calculations and experimental investigations were carried out for WO3-C and W-C systems, and a formation mechanism was proposed. In the results, for the synthesis of WC, the use of over stoichiometric amount of C together with a specially assembled experimental setup (which effectively retains heat in the system) is necessary. The WC powder is successfully obtained by heating WO3:5C mixture for 900 s in a domestic microwave oven.

  13. Evaluation the microwave heating of spinel crystals in high-level waste glass

    SciTech Connect

    Christian, J. H.; Washington, A. L.

    2015-08-18

    In this report, the microwave heating of a crystal-free and a partially (24 wt%) trevorite-crystallized waste glass simulant were evaluated. The results show that a 500 mg piece of partially crystallized waste glass can be heated from room-temperature to above 1600 °C (as measured by infrared radiometry) within 2 minutes using a single mode, highly focused, 2.45 GHz microwave, operating at 300 W. X-ray diffraction measurements show that the partially crystallized glass experiences an 87 % reduction in trevorite following irradiation and thermal quenching. When a crystal-free analogue of the same waste glass simulant composition is exposed to the same microwave radiation it could not be heated above 450 °C regardless of the heating time.

  14. Practical evaluations on heating characteristics of thin microwave antenna for intracavitary thermal therapy.

    PubMed

    Saito, Kazuyuki; Tsubouchi, Kousuke; Takahashi, Masaharu; Ito, Koichi

    2010-01-01

    Microwave thermal therapy is one of the modalities for cancer treatment. There are several schemes of microwave heating. The authors have been studying thin coaxial antenna for intracavitary microwave heating aiming at the treatment of bile duct carcinoma. Up to now, the heating characteristics of the antenna are investigated by numerical simulation and experiment for finding a possibility of the treatment. In this study, in order to consider practical situations of the treatment, heating characteristics of the antenna inserted into a metallic stent is evaluated by numerical simulations. Moreover, the relation between coagulation size of the tissue and the radiation power from the antenna is investigated experimentally. It must be considered, when the input power of the antenna is high (around several tens of watts). From these investigations, some useful results for practical treatments were found.

  15. Method for curing polymers using variable-frequency microwave heating

    DOEpatents

    Lauf, Robert J.; Bible, Don W.; Paulauskas, Felix L.

    1998-01-01

    A method for curing polymers (11) incorporating a variable frequency microwave furnace system (10) designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity (34). By varying the frequency of the microwave signal, non-uniformities within the cavity (34) are minimized, thereby achieving a more uniform cure throughout the workpiece (36). A directional coupler (24) is provided for detecting the direction of a signal and further directing the signal depending on the detected direction. A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. The furnace cavity (34) may be adapted to be used to cure materials defining a continuous sheet or which require compressive forces during curing.

  16. Method for curing polymers using variable-frequency microwave heating

    DOEpatents

    Lauf, R.J.; Bible, D.W.; Paulauskas, F.L.

    1998-02-24

    A method for curing polymers incorporating a variable frequency microwave furnace system designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity is disclosed. By varying the frequency of the microwave signal, non-uniformities within the cavity are minimized, thereby achieving a more uniform cure throughout the workpiece. A directional coupler is provided for detecting the direction of a signal and further directing the signal depending on the detected direction. A first power meter is provided for measuring the power delivered to the microwave furnace. A second power meter detects the magnitude of reflected power. The furnace cavity may be adapted to be used to cure materials defining a continuous sheet or which require compressive forces during curing. 15 figs.

  17. Efficiency of Microwave Heating of Weakly Loaded Polymeric Nanocomposites (Postprint)

    DTIC Science & Technology

    2012-05-10

    shielding and radar absorption [5]. Interaction of carbon nanotubes with microwaves is a subject of active ongoing research, 2 and the...mechanism of the microwave absorption by carbon nanotubes is still poorly understood [6-8]. Low thermal conductivity materials with controlled...and RAS design simulation. Composites Science and Technology. 70(2): p. 400‐409. 6. Vázquez, E. and M. Prato, Carbon Nanotubes and

  18. Calibration of temperature measurement by infrared pyrometry in microwave heating of powder materials: an exothermic reaction based approach.

    PubMed

    Luo, S D; Yang, Y F; Schaffer, G B; Qian, M

    2013-01-01

    Accurate temperature measurement remains a challenge for microwave heating of powder materials. We propose a temperature calibration method based on exothermic reactions and the resultant thermal runaway that occurs during microwave heating. The approach was demonstrated on microwave heating of four titanium alloys. Differential scanning calorimetry was used to determine the threshold reaction temperature for each selected titanium alloy. This served as a standard for the microwave heating of these titanium alloys. Infrared pyrometric temperature measurements were then calibrated by comparing the starting temperature of each thermal runaway event with the threshold reaction temperature.

  19. Microwave absorption in powders of small conducting particles for heating applications.

    PubMed

    Porch, Adrian; Slocombe, Daniel; Edwards, Peter P

    2013-02-28

    In microwave chemistry there is a common misconception that small, highly conducting particles heat profusely when placed in a large microwave electric field. However, this is not the case; with the simple physical explanation that the electric field (which drives the heating) within a highly conducting particle is highly screened. Instead, it is the magnetic absorption associated with induction that accounts for the large experimental heating rates observed for small metal particles. We present simple principles for the effective heating of particles in microwave fields from calculations of electric and magnetic dipole absorptions for a range of practical values of particle size and conductivity. For highly conducting particles, magnetic absorption dominates electric absorption over a wide range of particle radii, with an optimum absorption set by the ratio of mean particle radius a to the skin depth δ (specifically, by the condition a = 2.41δ). This means that for particles of any conductivity, optimized magnetic absorption (and hence microwave heating by magnetic induction) can be achieved by simple selection of the mean particle size. For weakly conducting samples, electric dipole absorption dominates, and is maximized when the conductivity is approximately σ ≈ 3ωε(0) ≈ 0.4 S m(-1), independent of particle radius. Therefore, although electric dipole heating can be as effective as magnetic dipole heating for a powder sample of the same volume, it is harder to obtain optimized conditions at a fixed frequency of microwave field. The absorption of sub-micron particles is ineffective in both magnetic and electric fields. However, if the particles are magnetic, with a lossy part to their complex permeability, then magnetic dipole losses are dramatically enhanced compared to their values for non-magnetic particles. An interesting application of this is the use of very small magnetic particles for the selective microwave heating of biological samples.

  20. Improvement of coal water slurry property through coal physicochemical modifications by microwave irradiation and thermal heat

    SciTech Connect

    Jun Cheng; Junhu Zhou; Yanchang Li; Jianzhong Liu; Kefa Cen

    2008-07-15

    To improve the coal water slurry (CWS) property made from Chinese Shenhua coal with high inherent moisture and oxygen contents, microwave irradiation and thermal heat were employed to modify the coal physicochemical property. Microwave irradiation reduces the inherent moisture and reforms the oxygenic function groups, while it decreases the total specific surface area. Thermal heat markedly decreases the inherent moisture, volatile, and oxygen contents, while it dramatically increases the total specific surface area. Therefore, microwave irradiation gives a higher CWS concentration and a better rheological behavior than thermal heat, while it remarkably reduces the operation time and energy consumption. The maximum CWS concentration given by microwave irradiation at 420 W for 60 s is 62.14%, which is not only higher than that of 60.41% given by thermal heat at 450{sup o}C for 0.5 h but also higher than the initial 58.23%. Meanwhile, the minimum shear stress given by microwave irradiation is 36.4 Pa at the shear rate of 100 s{sup -1}, which is not only lower than that of 42.4 Pa given by thermal heat but also lower than the initial 79.8 Pa. The minimum unit energy consumption of 0.115 kWh/(kg of coal) and electricity cost of 4.6 U.S. $/(ton of coal) for CWS concentration promotion by 1% are obtained at 420 W for 20 s in the microwave oven. The unit energy consumptions for CWS concentration promotion and inherent moisture removal by thermal heat are, respectively, 214 and 22.5 times higher than those by microwave irradiation, while the energy use efficiencies are on the converse. 27 refs., 11 figs., 2 tabs.

  1. An experimental study of waveguide coupled microwave heating with conventional multicusp negative ion sources

    NASA Astrophysics Data System (ADS)

    Komppula, J.; Kalvas, T.; Koivisto, H.; Laulainen, J.; Tarvainen, O.

    2015-04-01

    Negative ion production with conventional multicusp plasma chambers utilizing 2.45 GHz microwave heating is demonstrated. The experimental results were obtained with the multicusp plasma chambers and extraction systems of the RF-driven RADIS ion source and the filament driven arc discharge ion source LIISA. A waveguide microwave coupling system, which is almost similar to the one used with the SILHI ion source, was used. The results demonstrate that at least one third of negative ion beam obtained with inductive RF-coupling (RADIS) or arc discharge (LIISA) can be achieved with 1 kW of 2.45 GHz microwave power in CW mode without any modification of the plasma chamber. The co-extracted electron to H- ratio and the optimum pressure range were observed to be similar for both heating methods. The behaviour of the plasma implies that the energy transfer from the microwaves to the plasma electrons is mainly an off-resonance process.

  2. A Phase-Shifting Method for Improving the Heating Uniformity of Microwave Processing Materials

    PubMed Central

    Liao, Yinhong; Lan, Junqing; Zhang, Chun; Hong, Tao; Yang, Yang; Huang, Kama; Zhu, Huacheng

    2016-01-01

    Microwave processing of materials has been found to deliver enormous advantages over conventional processing methods in terms of mechanical and physical properties of the materials. However, the non-uniform temperature distribution is the key problem of microwave processing, which is related to the structure of the cavity, and the placement and physical parameters of the material. In this paper, a new microwave cavity structure with a sliding short based on phase-shifting heating is creatively proposed to improve the temperature uniformity. An electronic mathematical model based on the Finite Element Method (FEM) is built to predict the temperature distribution. Meanwhile, a new computational approach based on the theory of transformation optics is first provided to solve the problem of the moving boundary in the model simulation. At first, the experiment is carried out to validate the model, and heating results from the experiment show good agreement with the model’s prediction. Based on the verified model, materials selected among a wide range of dielectric constants are treated by stationary heating and phase-shifting heating. The coefficient of variation (COV) of the temperature and temperature difference has been compared in detail between stationary heating and phase-shifting heating. A significant improvement in heating uniformity can be seen from the temperature distribution for most of the materials. Furthermore, three other materials are also treated at high temperature and the heating uniformity is also improved. Briefly, the strategy of phase-shifting heating plays a significant role in solve the problem of non-uniform heating in microwave-based material processing. A 25%–58% increase in uniformity from adapting the phase-shifting method can be observed for the microwave-processed materials. PMID:28773433

  3. Microwave heating enhances antioxidant and emulsifying activities of ovalbumin glycated with glucose in solid-state.

    PubMed

    Tu, Zong-Cai; Hu, Yue-Ming; Wang, Hui; Huang, Xiao-Qin; Xia, Shi-Qi; Niu, Pei-Pei

    2015-03-01

    The aim of this study was to characterize the properties of ovalbumin (OVA) after glycated with glucose under microwave heating. For this purpose, microwave at 480 and 640 W power levels were used for heating the OVA-glucose system in solid-state for 0, 5, 10, 15, 20 and 25 min, respectively. The results indicated that the protein molecular weight was increased after glycated with glucose under microwave treatment, the pH of the system was decreased with the increase of microwave treatment power and time, while the UV absorbance, browning intensity, antioxidant activities as well as the emulsifying activity and emulsion stability of the Maillard reaction products (MRPs) were increased in according with the raise of microwave treatment power and time. The reaction time of microwave treatment is much shorter than those using traditional methods, suggesting that microwave irradiation is a novel and efficient approach to promote Maillard reaction (MR) in dry state and improve protein antioxidant and functional properties.

  4. Dielectric properties and carbothermic reduction of zinc oxide and zinc ferrite by microwave heating

    PubMed Central

    Fabritius, Timo; Heikkinen, Eetu-Pekka; Chen, Guo

    2017-01-01

    This paper aims to study the dielectric properties and carbothermic reduction of zinc oxide (zincite, ZnO) and zinc ferrite (franklinite, ZnFe2O4) by microwave heating. To achieve this aim, the dielectric properties were measured with an open-ended coaxial method to understand the behaviour of the samples under microwave irradiation. The effects of microwave power, duration time and sample mass on the heating rate, and the effects of the stoichiometric amount of graphite on the reduction of ZnO and decomposition of ZnFe2O4 were investigated. The results show that ZnFe2O4 has significantly higher dielectric properties compared to ZnO. Generally, for both samples, the dielectric values at room temperature were quite low, indicating that both ZnO and ZnFe2O4 are poor microwave absorbers. It was found that the temperatures have a more significant effect on the imaginary permittivities than on the real permittivities. The heating rate showed that the sample temperature increased with increase in microwave power and sample mass. Using 700 W of microwave power and two times the stoichiometric amount of graphite, almost complete reduction of ZnO was achieved in 12 min, while ZnFe2O4 completely decomposed to zincite and wustite in 3 min.

  5. Dielectric properties and carbothermic reduction of zinc oxide and zinc ferrite by microwave heating.

    PubMed

    Omran, Mamdouh; Fabritius, Timo; Heikkinen, Eetu-Pekka; Chen, Guo

    2017-09-01

    This paper aims to study the dielectric properties and carbothermic reduction of zinc oxide (zincite, ZnO) and zinc ferrite (franklinite, ZnFe2O4) by microwave heating. To achieve this aim, the dielectric properties were measured with an open-ended coaxial method to understand the behaviour of the samples under microwave irradiation. The effects of microwave power, duration time and sample mass on the heating rate, and the effects of the stoichiometric amount of graphite on the reduction of ZnO and decomposition of ZnFe2O4 were investigated. The results show that ZnFe2O4 has significantly higher dielectric properties compared to ZnO. Generally, for both samples, the dielectric values at room temperature were quite low, indicating that both ZnO and ZnFe2O4 are poor microwave absorbers. It was found that the temperatures have a more significant effect on the imaginary permittivities than on the real permittivities. The heating rate showed that the sample temperature increased with increase in microwave power and sample mass. Using 700 W of microwave power and two times the stoichiometric amount of graphite, almost complete reduction of ZnO was achieved in 12 min, while ZnFe2O4 completely decomposed to zincite and wustite in 3 min.

  6. Thermoelectric properties of bulk MoSi2 synthesized by solid state microwave heating

    NASA Astrophysics Data System (ADS)

    Lan, Yu; Xie, Mianyu; Ouyang, Ting; Yue, Song

    2016-07-01

    In this research, single phase α-MoSi2 was prepared by solid state hybrid microwave heating within 90 min at relatively low temperature 1273 K. Such precursor powders were then ball milled and sintered by microwave heating at different temperatures. The thermoelectric (TE) properties of MoSi2 bulks were investigated in the temperature range of 300-673 K. When the sintering temperature increases from 973 K to 1273 K, the electrical resistivity decreases significantly and the Seebeck coefficients increase obviously, leading to the maximum TE powder factor of 6.2 × 10-6Wm-1K-2 at 673 K. These results demonstrate the feasibility of high efficient and economical synthesis of MoSi2 by microwave heating technique, with the final products having comparable TE performance in comparison to those from typical methods with long duration and energy-extensive consumption.

  7. Conductive heating and microwave hydrolysis under identical heating profiles for advanced anaerobic digestion of municipal sludge.

    PubMed

    Mehdizadeh, Seyedeh Neda; Eskicioglu, Cigdem; Bobowski, Jake; Johnson, Thomas

    2013-09-15

    Microwave (2.45 GHz, 1200 W) and conventional heating (custom pressure vessel) pretreatments were applied to dewatered municipal waste sludge (18% total solids) using identical heating profiles that span a wide range of temperatures (80-160 °C). Fourteen lab-scale semi-continuous digesters were set up to optimize the energy (methane) output and sludge retention time (SRT) requirements of untreated (control) and thermally pretreated anaerobic digesters operated under mesophilic and thermophilic temperatures. Both pretreatment methods indicated that in the pretreatment range of 80-160 °C, temperature was a statistically significant factor (p-value < 0.05) for increasing solubilization of chemical oxygen demand and biopolymers (proteins, sugars, humic acids) of the waste sludge. However, the type of pretreatment method, i.e. microwave versus conventional heating, had no statistically significant effect (p-value >0.05) on sludge solubilization. With the exception of the control digesters at a 5-d SRT, all control and pretreated digesters achieved steady state at all three SRTs, corresponding to volumetric organic loading rates of 1.74-6.96 g chemical oxygen demand/L/d. At an SRT of 5 d, both mesophilic and thermophilic controls stopped producing biogas after 20 d of operation with total volatile fatty acids concentrations exceeding 1818 mg/L at pH <5.64 for mesophilic and 2853 mg/L at pH <7.02 for thermophilic controls, while the pretreated digesters continued producing biogas. Furthermore, relative (to control) organic removal efficiencies dramatically increased as SRT was shortened from 20 to 10 and then 5 d, indicating that the control digesters were challenged as the organic loading rate was increased. Energy analysis showed that, at an elevated temperature of 160 °C, the amount of methane recovered was not enough to compensate for the energy input. Among the digesters with positive net energy productions, control and pretreated digesters at 80 °C were more

  8. Gas heating effects on the formation and propagation of a microwave streamer in air

    NASA Astrophysics Data System (ADS)

    Kourtzanidis, Konstantinos; Rogier, François; Boeuf, Jean-Pierre

    2015-09-01

    The development of microwave plasma streamers at 110 GHz in atmospheric pressure air is numerically investigated taking into account the intense gas heating and its effects on the plasma formation and dynamics. The simulations are based on an implicit finite difference time domain formulation of Maxwell's equations coupled with a simple plasma fluid model and a real gas Euler equation solver. The numerical results show how the formation of a shock wave due to the large microwave power absorbed by the plasma and converted into gas heating strongly modifies the streamer elongation and dynamics. A microwave streamer filament stretches along its axis because of ionization-diffusion mechanisms in the enhanced electric field at the streamer tips. The change in the gas density distribution associated with the formation of shock wave due to gas heating strongly modifies the ionization and diffusion mechanisms and tends to limit the on-axis microwave streamer elongation by enhancing resonance effects. The simulations suggest that gas heating effects also play an important role in the observed bending or branching of microwave streamers after they have reached a critical length.

  9. Influence of microwave heating on fluoride, chloride, nitrate and sulfate concentrations in water.

    PubMed

    Figueiredo, Eduardo Costa; Dias, Jailson Cardoso; Kubota, Lauro Tatsuo; Korn, Mauro; Oliveira, Pedro Vitoriano; Arruda, Marco Aurélio Zezzi

    2011-10-15

    This paper describes a study about the influence of microwave radiation using closed vessels on fluoride, chloride, nitrate and sulfate concentrations in aqueous media. The experiments were processed by heating water using PFA vessels and a microwave cavity oven, determining the anions by ion chromatography. The influence of the exposure time, the atmospheric composition, the kind of heating (water bath or microwave radiation) and the possible formation of hydrogen peroxide were investigated. The limits of quantification for fluoride, chloride, nitrate and sulfate were respectively of 0.17, 0.15, 0.55 and 0.57 μg L(-1), and precision, expressed as RSD, was <4% for all considered anions. The hydrogen peroxide was quantified by spectrophotometry, and the limit of quantification and precision were 24 μg L(-1) and <5% (n=10), respectively. The results demonstrate a significant increase in the anion concentration levels (between 63 and 89%) when microwave heating was used in comparison with heating by water bath. In addition, these changes observed can be mainly attributed to the species transfers, either between gaseous (atmospheric gases) and liquid (water) phases for nitrate, or between vessels walls and water for fluoride, chloride and sulfate. Additionally, hydrogen peroxide concentration higher than 45 μg L(-1) was determined when water was exposed to microwave radiation.

  10. Absorption of intense microwaves and ion acoustic turbulence due to heat transport

    SciTech Connect

    De Groot, J.S.; Liu, J.M.; Matte, J.P.

    1994-02-04

    Measurements and calculations of the inverse bremsstrahlung absorption of intense microwaves are presented. The isotropic component of the electron distribution becomes flat-topped in agreement with detailed Fokker-Planck calculations. The plasma heating is reduced due to the flat-topped distributions in agreement with calculations. The calculations show that the heat flux at high microwave powers is very large, q{sub max} {approx} 0.3 n{sub e}v{sub e}T{sub e}. A new particle model to, calculate the heat transport inhibition due to ion acoustic turbulence in ICF plasmas is also presented. One-dimensional PIC calculations of ion acoustic turbulence excited due to heat transport are presented. The 2-D PIC code is presently being used to perform calculations of heat flux inhibition due to ion acoustic turbulence.

  11. Dual-mode antenna array for microwave heating and noninvasive thermometry of superficial tissue disease

    NASA Astrophysics Data System (ADS)

    Stauffer, Paul R.; Jacobsen, Svein; Rossetto, Francesca; Diederich, Chris J.; Neuman, Daniel

    1999-05-01

    Hyperthermia therapy of superficial skin disease has proven clinically useful, but current heating equipment is clumsy and technically inadequate for many patients. The present effort describes a dual purpose multielement conformal array microwave applicator that is fabricated from flexible printed circuit board (PCB) material to facilitate heating of large surface areas overlying contoured anatomy. Preliminary studies document the feasibility of combining concentric spiral microstrip antennas within multilayer PCB material in order to achieve tissue heating simultaneously with non-invasive thermometry by radiometric sensing of blackbody radiation from the target tissue under the applicator. Results demonstrate that superficial tissue regions may be heated uniformly above 50% of SARmax out to the periphery of 915 MHz conformal array applicators made from arrays of Dual Concentric Conductor apertures. Finally the data clearly demonstrate that separate complimentary antenna structures may be combined together in thin and lightweight conformal arrays to provide heating simultaneously with microwave radiometry based temperature monitoring of superficial tissue.

  12. Preliminary comparative studies of Thermus aquaticus resilience to thermal and microwave heat input

    NASA Astrophysics Data System (ADS)

    Kabza, Konrad; George, Karen; von Meer, Stella; Kargol, Armin

    2008-03-01

    Thermus aquaticus was grown using existing ATCC protocol. Bacteria were cultured in large batches and each batch partitioned into usable 250 mL aliquots. These samples were then tested using identical parallel experiments, one heated with a traditional thermal heat source, while the other was irradiated with a 2.45 GHz conventional microwave oven. Relative growth of the Thermus aquaticus was measured using UV visible spectroscopy at 400 nm. Multiple runs of the same experiments were averaged and the growth data for two modes of energization plotted. A unique low microwave exposure apparatus with a flow-through cell will be described and the entire experimental setup discussed.

  13. Size limitations for microwave cavity to simulate heating of blanket material in fusion reactor

    SciTech Connect

    Wolf, D.

    1987-01-01

    The power profile in the blanket material of a nuclear fusion reactor can be simulated by using microwaves at 200 MHz. Using these microwaves, ceramic breeder materials can be thermally tested to determine their acceptability as blanket materials without entering a nuclear fusion environment. A resonating cavity design is employed which can achieve uniform cross sectional heating in the plane transverse to the neutron flux. As the sample size increases in height and width, higher order modes, above the dominant mode, are propagated and destroy the approximation to the heating produced in a fusion reactor. The limits at which these modes develop are determined in the paper.

  14. The research of ceramic materials for applications in the glass industry including microwave heating techniques

    NASA Astrophysics Data System (ADS)

    Kogut, K.; Kasprzyk, K.; Zboromirska-Wnukiewicz, B.; Ruziewicz, T.

    2016-02-01

    The melting of a glass is a very energy-intensive process. Selection of energy sources, the heating technique and the method of heating recovery are a fundamental issue from the furnace design point of view of and economic effectiveness of the process. In these processes the problem constitutes the lack of the appropriate ceramic materials that would meet the requirements. In this work the standard ceramic materials were examined and verified. The possibilities of application of microwave techniques were evaluated. In addition the requirements regarding the parameters of new ceramic materials applied for microwave technologies were determined.

  15. Mechanism for microwave heating of 1-(4‧-cyanophenyl)-4-propylcyclohexane characterized by in situ microwave irradiation NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Tasei, Yugo; Yamakami, Takuya; Kawamura, Izuru; Fujito, Teruaki; Ushida, Kiminori; Sato, Motoyasu; Naito, Akira

    2015-05-01

    Microwave heating is widely used to accelerate organic reactions and enhance the activity of enzymes. However, the detailed molecular mechanism for the effect of microwave on chemical reactions is not yet fully understood. To investigate the effects of microwave heating on organic compounds, we have developed an in situ microwave irradiation NMR spectroscopy. 1H NMR spectra of 1-(4‧-cyanophenyl)-4-propylcyclohexane (PCH3) in the liquid crystalline and isotropic phases were observed under microwave irradiation. When the temperature was regulated at slightly higher than the phase transition temperature (Tc = 45 °C) under a gas flow temperature control system, liquid crystalline phase mostly changed to the isotropic phase. Under microwave irradiation and with the gas flow temperature maintained at 20 °C, which is 25 °C below the Tc, the isotropic phase appeared stationary as an approximately 2% fraction in the liquid crystalline phase. The temperature of the liquid crystalline state was estimated to be 38 °C according to the line width, which is at least 7 °C lower than the Tc. The temperature of this isotropic phase should be higher than 45 °C, which is considered to be a non-equilibrium local heating state induced by microwave irradiation. Microwaves at a power of 195 W were irradiated to the isotropic phase of PCH3 at 50 °C and after 2 min, the temperature reached 220 °C. The temperature of PCH3 under microwave irradiation was estimated by measurement of the chemical shift changes of individual protons in the molecule. These results demonstrate that microwave heating generates very high temperature within a short time using an in situ microwave irradiation NMR spectrometer.

  16. Investigation on microwave heating for direct leaching of chalcopyrite ores and concentrates

    NASA Astrophysics Data System (ADS)

    Onol, Kubra; Saridede, Muhlis Nezihi

    2013-03-01

    The use of microwave energy in materials processing is a relatively new development presenting numerous advantages because of the rapid heating feature. Microwave technology has great potential to improve the extraction efficiency of metals in terms of both a reduction in required leaching time and an increase in the recovery of valuable metals. This method is especially pertinent in view of the increased demand for environment-friendly processes. In the present study, the influence of microwave heating on the direct leaching of chalcopyrite ores and concentrates were investigated. The results of microwave leaching experiments were compared with those obtained under conventional conditions. During these processes, parameters such as leaching media, temperature, and time have been worked to determine the optimum conditions for proper copper dissolution. Experimental results show that microwave leaching is more efficient than conventional leaching. The optimum leaching conditions for microwave leaching are the solid-to-liquid ratio of 1:100 g/mL, the temperature of 140°C, the solution of 0.5 M H2SO4 + 0.05 M Fe2(SO4)3, and the time of 1 h.

  17. Development of heating method by microwave for sterilization of bone allografts.

    PubMed

    Uchiyama, Katsufumi; Ujihira, Masanobu; Mabuchi, Kiyoshi; Takahira, Naonobu; Komiya, Koichiro; Itoman, Moritoshi

    2005-01-01

    The purpose of this study was to develop a disinfection method using a microwave apparatus to treat large bone allografts. Heating of a bone allograft is an effective method for the disinfection of bacteria or inactivation of viruses. However, the size of the bone we can treat is limited, and following the popular method of using a bathtub is a lengthy process. The experimental system described here was designed using a microwave oven, an optical-fiber thermometer, and a power regulator. Large and small specimens, a femoral head, and a metatarsal were harvested from a bovine femur. The influence of size and the electrical or thermal characteristics of the specimens were assessed regarding temperature distribution after microwave irradiation. The effects of humidity or hot-air supply were also assessed. The average temperature of the bovine femoral head became 80 degrees C throughout the 15 min of microwave irradiation, although the temperature in the metatarsal did not attain uniformity. Microwave irradiation with a hot-air supply realized a uniform distribution of temperature at 83.0 degrees +/- 0.4 degrees C in the metatarsal within 15 min. Use of microwave irradiation enables quick heating for disinfection of large allograft bones when a hot-air supply was used as well.

  18. A microwave and ohmic combination heater for uniform heating of liquid-particle food mixtures.

    PubMed

    Choi, Won; Nguyen, Loc T; Lee, Seung Hyun; Jun, Soojin

    2011-01-01

    Microwave and ohmic combination heating was proposed to improve the uniformity of thermal processing of particulate foods. Thermal patterns of a liquid-particle mixture in a small test cell were studied using both experimental and simulation approaches. Carrot cubes (10 mm × 10 mm × 10 mm) and 0.1% NaCl salt solution were used as model foods. The temperature distribution of solid and liquid phases was examined using individual and combination heating methods. Under ohmic heating, the liquid was heated faster by 18.9 °C after 250 s. The heating rate of a carrot cube was faster than liquid under microwave heating and temperature rise of carrot was approximately 11.2 °C higher than that of solution after heating of 70 s. Samples experienced different heating patterns over time during the combination heating. Carrot samples showed a thermal lead initially when heated under microwave and the trend reversed during the second stage when ohmic heating was applied. Liquid-particle temperature difference was reduced as the combination heating proceeded, and came to be less than 2 °C at the end. Results obtained from simulation showed similar patterns and all prediction data agreed well with the experimental data. The prediction errors for sample temperatures ranged from 5.7% to 11.6%. The results provided better understanding for designing a continuous flow combination heater that can produce uniform temperature of solid-liquid mixtures. If successful, this combination heating technique will find its way to effective aseptic or sterile processing of low acid multiphase foods containing large particulates (such as soups with meatballs or vegetables) that has not been a commercial reality in the United States. © 2011 Institute of Food Technologists®

  19. Experimental study of temperature distribution in rubber material during microwave heating and vulcanization process

    NASA Astrophysics Data System (ADS)

    Chen, Hai-Long; Li, Tao; Liang, Yun; Sun, Bin; Li, Qing-Ling

    2016-07-01

    Microwave technology has been employed to heat sheet rubber, the optical fiber temperature online monitor and optical fiber temperature sensor have been employed to measure the temperature in sheet rubber. The temperature of sheet rubber increased with increase of heating time during microwave heating process in which the maximum of temperature was <100 °C and microwave vulcanization process in which the maximum of temperature was <150 °C, the curves of temperature-time presented nonlinearity. The rate of temperature rising in central zone of sheet rubber was higher than the rate of temperature rising in marginal zone of sheet rubber, and the final temperature in central zone of sheet rubber was also higher than the final temperature in marginal zone of sheet rubber. In the microwave heating and vulcanization process of sheet rubber, the maximum of rate of temperature rising and the maximum of temperature belong to the central zone of sheet rubber, so the distribution of electric field was uneven in heating chamber, which led to the uneven temperature distribution of sheet rubber. The higher electric field intensity value converges on the central zone of sheet rubber.

  20. Finite Element Analysis of Three Methods for Microwave Heating of Planetary Surfaces

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin; Kaukler, William

    2012-01-01

    In-Situ Resource Utilization will be Ground Breaking technology for sustained exploration of space. Volatiles are present in planetary regolith, but water by far has the most potential for effective utilization. The presence of water at the lunar poles and Mars opens the possibility of using the hydrogen for propellant on missions beyond Earth orbit. Likewise, the oxygen could be used for in-space propulsion for lunar ascent/descent and for space tugs from low lunar orbit to low Earth orbit. Water is also an effective radiation shielding material as well as a valuable expendable (water and oxygen) required for habitation in space. Because of the strong function of water vapor pressure with temperature, heating regolith effectively liberates water vapor by sublimation. Microwave energy will penetrate soil and heat from within, much more efficiently than heating from the surface with radiant heat. This is especially true under vacuum conditions since the heat transfer rate is very low. The depth of microwave penetration is a strong function of the microwave frequency and to a lesser extent on regolith dielectric properties. New methods for delivery of microwaves into lunar and planetary surfaces is being prototyped with laboratory experiments and modeled with COMSOL MultiPhysics. Recent results are discussed.

  1. A comparative study of infrared and microwave heating for microbial decontamination of paprika powder

    PubMed Central

    Eliasson, Lovisa; Isaksson, Sven; Lövenklev, Maria; Ahrné, Lilia

    2015-01-01

    There is currently a need in developing new decontamination technologies for spices due to limitations of existing technologies, mainly regarding their effects on spices’ sensory quality. In the search of new decontamination solutions, it is of interest to compare different technologies, to provide the industry with knowledge for taking decisions concerning appropriate decontamination technologies for spices. The present study compares infrared (IR) and microwave decontamination of naturally contaminated paprika powder after adjustment of water activity to 0.88. IR respectively microwave heating was applied to quickly heat up paprika powder to 98°C, after which the paprika sample was transferred to a conventional oven set at 98°C to keep the temperature constant during a holding time up to 20 min. In the present experimental set-up microwave treatment at 98°C for 20 min resulted in a reduction of 4.8 log units of the total number of mesophilic bacteria, while the IR treatment showed a 1 log unit lower reduction for the corresponding temperature and treatment time. Microwave and IR heating created different temperature profiles and moisture distribution within the paprika sample during the heating up part of the process, which is likely to have influenced the decontamination efficiency. The results of this study are used to discuss the difficulties in comparing two thermal technologies on equal conditions due to differences in their heating mechanisms. PMID:26483783

  2. Combined chromatographic and mass spectrometric toolbox for fingerprinting migration from PET tray during microwave heating.

    PubMed

    Alin, Jonas; Hakkarainen, Minna

    2013-02-13

    A combined chromatographic and mass spectrometric toolbox was utilized to determine the interactions between poly(ethylene terephthalate) (PET) food packaging and different food simulants during microwave heating. Overall and specific migration was determined by combining weight loss measurements with gas chromatography-mass spectrometry (GC-MS) and electrospray ionization mass spectrometry (ESI-MS). This allowed mapping of low molecular weight migrants in the molecular range up to 2000 g/mol. Microwave heating caused significantly faster migration of cyclic oligomers into ethanol and isooctane as compared to migration during conventional heating at the same temperature. This effect was more significant at lower temperature at which diffusion rates are generally lower. It was also shown that transesterification took place between PET and ethanol during microwave heating, leading to formation of diethyl terephthalate. The detected migrants included cyclic oligomers from dimer to hexamer, in most cases containing extra ethylene glycol units, and oxidized Irgafos 168. ESI-MS combined with CID MS-MS was an excellent tool for structural interpretation of the nonvolatile compounds migrating to the food simulants. The overall migration was below the overall migration limit of 10 mg/dm(2) set by the European commission after 4 h of microwave heating at 100 °C in all studied food simulants.

  3. Experimental study of temperature distribution in rubber material during microwave heating and vulcanization process

    NASA Astrophysics Data System (ADS)

    Chen, Hai-Long; Li, Tao; Liang, Yun; Sun, Bin; Li, Qing-Ling

    2017-03-01

    Microwave technology has been employed to heat sheet rubber, the optical fiber temperature online monitor and optical fiber temperature sensor have been employed to measure the temperature in sheet rubber. The temperature of sheet rubber increased with increase of heating time during microwave heating process in which the maximum of temperature was <100 °C and microwave vulcanization process in which the maximum of temperature was <150 °C, the curves of temperature-time presented nonlinearity. The rate of temperature rising in central zone of sheet rubber was higher than the rate of temperature rising in marginal zone of sheet rubber, and the final temperature in central zone of sheet rubber was also higher than the final temperature in marginal zone of sheet rubber. In the microwave heating and vulcanization process of sheet rubber, the maximum of rate of temperature rising and the maximum of temperature belong to the central zone of sheet rubber, so the distribution of electric field was uneven in heating chamber, which led to the uneven temperature distribution of sheet rubber. The higher electric field intensity value converges on the central zone of sheet rubber.

  4. Experimental and numerical evaluations on palm microwave heating for Red Palm Weevil pest control

    NASA Astrophysics Data System (ADS)

    Massa, Rita; Panariello, Gaetano; Pinchera, Daniele; Schettino, Fulvio; Caprio, Emilio; Griffo, Raffaele; Migliore, Marco Donald

    2017-03-01

    The invasive Red Palm Weevil is the major pest of palms. Several control methods have been applied, however concern is raised regarding the treatments that can cause significant environmental pollution. In this context the use of microwaves is particularly attractive. Microwave heating applications are increasingly proposed in the management of a wide range of agricultural and wood pests, exploiting the thermal death induced in the insects that have a thermal tolerance lower than that of the host matrices. This paper describes research aiming to combat the Red Palm pest using microwave heating systems. An electromagnetic-thermal model was developed to better control the temperature profile inside the palm tissues. In this process both electromagnetic and thermal parameters are involved, the latter being particularly critical depending on plant physiology. Their evaluation was carried out by fitting experimental data and the thermal model with few free parameters. The results obtained by the simplified model well match with both that of a commercial software 3D model and measurements on treated Phoenix canariensis palms with a ring microwave applicator. This work confirms that microwave heating is a promising, eco-compatible solution to fight the spread of weevil.

  5. Experimental and numerical evaluations on palm microwave heating for Red Palm Weevil pest control

    PubMed Central

    Massa, Rita; Panariello, Gaetano; Pinchera, Daniele; Schettino, Fulvio; Caprio, Emilio; Griffo, Raffaele; Migliore, Marco Donald

    2017-01-01

    The invasive Red Palm Weevil is the major pest of palms. Several control methods have been applied, however concern is raised regarding the treatments that can cause significant environmental pollution. In this context the use of microwaves is particularly attractive. Microwave heating applications are increasingly proposed in the management of a wide range of agricultural and wood pests, exploiting the thermal death induced in the insects that have a thermal tolerance lower than that of the host matrices. This paper describes research aiming to combat the Red Palm pest using microwave heating systems. An electromagnetic-thermal model was developed to better control the temperature profile inside the palm tissues. In this process both electromagnetic and thermal parameters are involved, the latter being particularly critical depending on plant physiology. Their evaluation was carried out by fitting experimental data and the thermal model with few free parameters. The results obtained by the simplified model well match with both that of a commercial software 3D model and measurements on treated Phoenix canariensis palms with a ring microwave applicator. This work confirms that microwave heating is a promising, eco-compatible solution to fight the spread of weevil. PMID:28361964

  6. Diversity-oriented synthesis and solid-phase organic synthesis under controlled microwave heating.

    PubMed

    Dai, Wei-Min; Shi, Jianyu

    2007-12-01

    Diversity-oriented organic synthesis (DOS) and solid-phase organic synthesis (SPOS) are proven technologies for generating small molecule libraries for chemical genetics studies. Integration of controlled microwave heating with DOS and SPOS not only speeds up the library preparation process but also offers unique opportunities in tackling issues which are hardly addressed by thermal heating. Microwave-assisted synthesis is illustrated for (a) highly regioselective Wittig olefination of cycloalkanones by accurate regulation of temperature; (b) tandem Wittig-IMDA sequence toward stereochemical diversity of gamma-butyrolactones; (c) one-pot alkylation-amidation approach toward appendage diversity through use of building blocks; and (d) one-pot U-4CR-annulation strategy toward skeletal diversity via careful reaction design. Microwave-assisted solid-phase organic synthesis (MASPOS) is highlighted by incorporating with split-pool combinatorial synthesis (SPCS) of indole sulfonamides via a key on-resin Cu(II)- or Pd(II)-catalyzed heteroannulation under microwave heating. Design and fabrication of a novel diglycine-derived catlinker are described and its role in facilitating on-resin reaction is evaluated. A traceless synthesis of indole sulfonamides via microwave-assisted Cu(II)-catalyzed heteroannulation of the catlinker-tethered substrates is also given.

  7. Synthesis of Rutile TiO2 from Panzhihua Sulfate Titanium Slag by Microwave Heating

    NASA Astrophysics Data System (ADS)

    Chen, Hufei; Chen, Guo; Wu, Yunqi; Peng, Jinhui; Srinivasakannan, C.; Chen, Jin

    2017-08-01

    This study aimed to assess the utilization of microwave heating for synthesis of rutile TiO2 by employing sulfate titanium slag produced by Panzhihua Iron and Steel Research Institute. To this end, the properties of sulfate titanium slag before and after microwave treatment, i.e., its crystal structure, surface microstructure, and surface chemical functional groups, were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transformation infrared (FT-IR) spectroscopy, respectively. Results of XRD analysis showed that the anosovite phase of the sulfate titanium slag transformed to the rutile TiO2 phase under microwave heating at 1100°C for duration of 120 min. Correspondingly, the SEM images revealed that the surface of the sulfate titanium slag grew as a granular substance after microwave roasting. The granular substance was observed to be rutile TiO2 with a rod-shaped structure. FT-IR spectra demonstrated the occurrence of a blue shift at 472.15 cm-1, indicating phase transformation from anosovite to rutile TiO2 because of the roasting process. From the experimental results, it is concluded that microwave heating can be an effective and efficient approach for the synthesis of synthetic rutile TiO2 from sulfate titanium slag.

  8. Determination of volatile chemicals released from microwave-heat-susceptor food packaging.

    PubMed

    McNeal, T P; Hollifield, H C

    1993-01-01

    Microwave heat susceptors that convert electromagnetic energy to heat attain high temperatures that make it possible to cook some foods to golden crispness in a microwave oven. Susceptors are typically packaged with foods intended for microwave use, e.g., waffles, pizzas, and french fries. The high temperatures > 302 degrees F used to cook some foods release trace levels of volatile chemicals from metalized polyester film, adhesive, and paper packaging materials; these volatile chemicals may be absorbed by the food. We simulated microwave susceptor cooking conditions and developed protocols by using headspace concentration capillary gas chromatography and mass spectrometry to identify volatile chemicals released from heated susceptors. We purchased a limited, cross-sectional sample of local retail microwave food products packaged with susceptors and used our protocol to analyze 10 different susceptor products. Although more than 140 unique chromatographic peaks were tabulated, only 44 volatile chemicals were identified, including 1,1,1-trichloroethane, benzene, and 2-(2-butoxyethoxy)ethanol, which were derived primarily from the paper and adhesive susceptor components. No one susceptor contained all the identified substances. The standard additions technique was the preferred method for quantitation. Trichloroethane and 2-(2-butoxyethoxy)ethanol were present in several products at 75-122 micrograms/in.2 of susceptor surface area. Benzene was found in 3 susceptors at < or = 0.22 microgram/in.2 levels. Examination indicates that adhesives used in more recent susceptor products were reformulated to remove even this trace level of benzene.

  9. Atmospheric Latent Heating Distributions in the Tropics Derived from Satellite Passive Microwave Radiometer Measurements.

    NASA Astrophysics Data System (ADS)

    Olson, William S.; Kummerow, Christian D.; Hong, Ye; Tao, Wei-Kuo

    1999-06-01

    A method for the remote sensing of three-dimensional latent heating distributions in precipitating tropical weather systems from satellite passive microwave observations is presented. In this method, cloud model simulated hydrometeor/latent heating vertical profiles that have radiative characteristics consistent with a given set of multispectral microwave radiometric observations are composited to create a best estimate of the observed profile. An estimate of the areal coverage of convective precipitation within the radiometer footprint is used as an additional constraint on the contributing model profiles. This constraint leads to more definitive retrieved profiles of precipitation and latent heating in synthetic data tests.The remote sensing method is applied to Special Sensor Microwave/Imager (SSM/I) observations of tropical systems that occurred during the TOGA COARE Intensive Observing Period, and to observations of Hurricane Andrew (1992). Although instantaneous estimates of rain rates are high-biased with respect to coincident radar rain estimates, precipitation patterns are reasonably correlated with radar patterns, and composite rain rate and latent heating profiles show respectable agreement with estimates from forecast models and heat and moisture budget calculations. Uncertainties in the remote sensing estimates of precipitation/latent heating may be partly attributed to the relatively low spatial resolution of the SSM/I and a lack of microwave sensitivity to tenuous anvil cloud, for which upper-tropospheric latent heating rates may be significant. Estimated latent heating distributions in Hurricane Andrew exhibit an upper-level heating maximum that strengthens as the storm undergoes a period of intensification.

  10. Fundamental Study on Localized Heating in Hyperthermia Using Phase Control of Long-wavelength Microwaves

    NASA Astrophysics Data System (ADS)

    Matsumoto, Hiroshi; Ishida, Hiroki; Nakamoto, Satoshi; Takeno, Hiromasa; Yasaka, Yasuyoshi; Kawai, Shigeaki; Mitani, Tomohiko; Shinohara, Naoki; Namiki, Hironori

    For the treatment of cancer using hyperthermia, high frequency electromagnetic fields are used to heat the cancer cells. These electromagnetic fields fall into two general frequency ranges, one relatively low, and the other in the microwave range. Both produce some side effects such as the heating of healthy cells or the impact on the body of invasive surgery required to expose deep-lying cells. To reduce these side reactions, the use of lower microwave frequencies with phase control was proposed. In this paper, we present a very basic study to prove the viability of the proposed scheme. This includes the selection of a suitable frequency, demonstration of localized heating using the selected frequency, and a three-dimensional numerical analysis of the electromagnetic fields involved. In the heating demonstration, a tissue-equivalent phantom made from agar was irradiated by phase-controlled electromagnetic waves from a pair of circular patch antennas operating at 430MHz. This produced localized heating. The numerical analysis produced a field distribution that corresponded closely to the results from the heating experiment. It confirmed that the phase control technique for long-wavelength microwaves was effective in producing localized heating.

  11. Microwave heated resin injector for advanced composite production.

    PubMed

    Stanculovic, Sebastijan; Feher, Lambert

    2008-01-01

    A novel microwave (MW) injector at 2.45 GHz for resin infiltration has been developed at the Institute for Pulsed Power and Microwave Technology (IHM), Research Center Karlsruhe (FZK), Germany. Resin injection is an essential step in the production of carbon fibre reinforced plastics (CFRP) for aerospace applications. A compact, low-cost and automated MW injector provides an efficient and safe energy transfer from the MW source to the resin and supports an appropriate electromagnetic field structure for homogeneous infiltration. The system provides temperature monitoring and an automatized MW power switching, which ensures a fast response of the MW system to rapid changes in the temperature for high flow rates of the resin. In low power measurements with a vector network analyzer, the geometry of the injector cavity has been adjusted to provide an efficient system. The MW injector has been tested for specific resin systems infiltrations.

  12. Quantification of carbon nanotubes in different environmental matrices by a microwave induced heating method.

    PubMed

    He, Yang; Al-Abed, Souhail R; Dionysiou, Dionysios D

    2017-02-15

    Carbon nanotubes (CNTs) have been incorporated into numerous consumer products, and have also been employed in various industrial areas because of their extraordinary properties. The large scale production and wide applications of CNTs make their release into the environment a major concern. Therefore, it is crucial to determine the degree of potential CNT contamination in the environment, which requires a sensitive and accurate technique for selectively detecting and quantifying CNTs in environmental matrices. In this study, a simple device based on utilizing heat generated/temperature increase from CNTs under microwave irradiation was built to quantify single-walled CNTs (SWCNTs), multi-walled CNTs (MWCNTs) and carboxylated CNTs (MWCNT-COOH) in three environmentally relevant matrices (sand, soil and sludge). Linear temperature vs CNT mass relationships were developed for the three environmental matrices spiked with known amounts of different types of CNTs that were then irradiated in a microwave at low energies (70-149W) for a short time (15-30s). MWCNTs had a greater microwave response in terms of heat generated/temperature increase than SWCNTs and MWCNT-COOH. An evaluation of microwave behavior of different carbonaceous materials showed that the microwave measurements of CNTs were not affected even with an excess of other organic, inorganic carbon or carbon based nanomaterials (fullerene, granular activated carbon and graphene oxide), mainly because microwave selectively heats materials such as CNTs that have a higher dielectric loss factor. Quantification limits using this technique for the sand, soil and sludge were determined as low as 18.61, 27.92, 814.4μg/g for MWCNTs at a microwave power of 133W and exposure time of 15s.

  13. Mathematical model of thermal spikes in microwave heating of ceramic oxide fibers

    SciTech Connect

    Thomas, J.R. Jr.; Unruh, W.P.; Vogt, G.J.

    1994-04-01

    Experiments on microwave sintering of ceramic fibers in a single-mode cavity have revealed the presence of thermal spikes and `hot spots` which sometimes travel along the fiber and eventually disappear. They are triggered by relatively small increases in microwave power, and thus have obvious implications for the development of practical microwave-based fiber processing systems. These hot spots are conjectured to originate at slight irregularities in the tow morphology, and propagate as the result of solid phase transitions which take place at elevated temperatures and reduce the dielectric loss coefficient {epsilon}{double_prime}. An elementary mathematical model of the heat transfer process was developed which reproduces the essential features of the observed phenomena, thus lending support to the conjecture. This model is based on the assumption of one-dimensional heat conduction along the axis of the fiber tow, and radiation losses at the surface.

  14. Microwave Heating as an Alternative Quarantine Method for Disinfestation of Stored Food Grains

    PubMed Central

    Kumar, Girish; Shah, Narendra G.

    2013-01-01

    Insects and pests constitute a major threat to food supplies all over the world. Some estimates put the loss of food grains because of infestation to about 40% of the world production. Contemporary disinfestation methods are chemical fumigation, ionizing radiation, controlled atmosphere, conventional hot air treatment, and dielectric heating, that is, radio frequency and microwave energy, and so forth. Though chemical fumigation is being used extensively in stored food grains, regulatory issues, insect resistance, and environmental concerns demand technically effective and environmentally sound quarantine methods. Recent studies have indicated that microwave treatment is a potential means of replacing other techniques because of selective heating, pollution free environment, equivalent or better quality retention, energy minimization, and so forth. The current paper reviews the recent advances in Microwave (MW) disinfestation of stored food products and its principle and experimental results from previous studies in order to establish the usefulness of this technology. PMID:26904615

  15. Rapid PCR amplification using a microfluidic device with integrated microwave heating and air impingement cooling.

    PubMed

    Shaw, Kirsty J; Docker, Peter T; Yelland, John V; Dyer, Charlotte E; Greenman, John; Greenway, Gillian M; Haswell, Stephen J

    2010-07-07

    A microwave heating system is described for performing polymerase chain reaction (PCR) in a microfluidic device. The heating system, in combination with air impingement cooling, provided rapid thermal cycling with heating and cooling rates of up to 65 degrees C s(-1) and minimal over- or under-shoot (+/-0.1 degrees C) when reaching target temperatures. In addition, once the required temperature was reached it could be maintained with an accuracy of +/-0.1 degrees C. To demonstrate the functionality of the system, PCR was successfully performed for the amplification of the Amelogenin locus using heating rates and quantities an order of magnitude faster and smaller than current commercial instruments.

  16. A comparative study of acrylamide formation induced by microwave and conventional heating methods.

    PubMed

    Yuan, Y; Chen, F; Zhao, G-H; Liu, J; Zhang, H-X; Hu, X-S

    2007-05-01

    In this study, the formation of acrylamide upon treatment with microwave and conventional heating, boiling, or frying was investigated in both Asn/Fru and Asn/Glc model systems and in potato chips. Acrylamide levels were analyzed by HPLC method, which was confirmed by HPLC-MS/MS. Present results in model systems showed that pH value had a complex influence on the formation of acrylamide in the 2 systems during both microwaving (600 W) and boiling (120 +/- 1 degrees C). At pH < 8.0, acrylamide content increased with increasing the pH value, reaching the maximum at pH 8.0 whereas acrylamide content decreased with the increase of pH. Regardless of pH and heating methods, acrylamide content generally increased with increasing treatment time. Surprisingly, all present results showed that microwave heating not only induced acrylamide formation in the 2 model systems but also facilitated more acrylamide to be formed as compared to the boiling method at identical pH and treatment time. At pH 4.0, 8.0, and 10.0, the larger the microwave power, the more the acrylamide content. Consistent with the above observation, treatment of potato chips with microwave heating for 2.5 to 3.5 min in the range 550 to 750 W similarly resulted in acrylamide formation. The highest acrylamide content was formed by 750 W microwave treatment as 0.897 +/- 0.099 mg/kg, which was significantly higher than that produced by traditional frying (180 +/- 1 degrees C), 0.645 +/- 0.035 mg/kg (P < 0.05).

  17. Synergistic effect of microwave heating and hydrogen peroxide on inactivation of microorganisms.

    PubMed

    Kuchma, T

    1998-01-01

    Escherichia coli K-12 isogenous strains and Pseudomonas aeruginosa 102 were used to study the synergistic effects of combined microwave heating at short-time processing with low concentrations of hydrogen peroxide. The effect of microwave heating to temperatures of 40, 50 and 60 degrees C, as well as the concentration of hydrogen peroxide (0.05, 0.08 and 0.1%), the sequence of the agents' use, the nature of microorganisms on the survival of cells, DNA damages and interaction factors were studied. A method of anomalous viscosity time dependencies (AVTD) was used for measurement of the changes of genome conformational state (GCS) simultaneously with bacterial survival determination. The synergistic effect of microwave heating and low concentrations of hydrogen peroxide was observed under combined application, and reached a maximum when the cells were exposed to microwave heating to 50 degrees C and 0.08% hydrogen peroxide simultaneously. Both maxima of cell destruction and DNA injuries have been achieved by successive exposure to (MW + 10 min H2O2) to 60 degrees C and 0.08% hydrogen peroxide. The mechanisms of synergistic effects, the role of a disturbance of DNA repair and the interaction of sublethal injuries caused by different agents are discussed.

  18. Sustainable synthesis of chemical entities by microwave heating with nano-catalysis in water

    EPA Science Inventory

    •Sustainable synthesis of chemical entities by microwave heating with nano-catalysis in water •CRADA’s with the private companies, CEM corporation and VeruTEK Technologies •Green Chemistry principles are accommodated via multi-faceted approach. Learning from nature- using na...

  19. Tolazoline decreases survival time during microwave-induced lethal heat stress in anesthetized rats

    SciTech Connect

    Jauchem, J.R.; Chang, K.S.; Frei, M.R.

    1996-03-01

    Effects of {alpha}-adrenergic antagonists have been studied during environmental heating but not during microwave-induced heating. Tolazoline may exert some of its effects via {alpha}-adrenergic blockade. In the present study, ketamine-anesthetized Sprague-Dawley rats were exposed to 2450-MHz microwaves at an average power density of 60 mW/cm{sup 2} (whole-body specific absorption rate of approximately 14 W/kg) until lethal temperatures were attained. The effects of tolazoline (10 mg/kg body weight) on physiological responses (including changes in body temperature, heart rate, blood pressure, and respiratory rate) were examined. Survival time was significantly shorter in the tolazoline group than in saline-treated animals. In general, heart rate and blood pressure responses were similar to those that occur during environmental heat stress. Heart rate, however, was significantly elevated in animals that received tolazoline, both before and during terminal microwave exposure. It is possible that changes associated with the elevated heart rate (e.g., less cardiac filling) in tolazoline-treated animals resulted in greater susceptibility to microwave-induced heating and the lower survival time. 47 refs., 3 figs., 2 tabs.

  20. Sustainable synthesis of chemical entities by microwave heating with nano-catalysis in water

    EPA Science Inventory

    •Sustainable synthesis of chemical entities by microwave heating with nano-catalysis in water •CRADA’s with the private companies, CEM corporation and VeruTEK Technologies •Green Chemistry principles are accommodated via multi-faceted approach. Learning from nature- using na...

  1. Microwave-based laboratory experiments for internally-heated mantle convection

    NASA Astrophysics Data System (ADS)

    Limare, A.; Surducan, E.; Surducan, V.; Neamtu, C.; di Giuseppe, E.; Vilella, K.; Farnetani, C. G.; Kaminski, E.; Jaupart, C.

    2013-11-01

    The thermal evolution of terrestrial planets is mainly controlled by the amount of radioactive heat sources in their mantle, and by the geometry and efficiency of solid state thermo-chemical convection within. So far, these systems have been studied using numerical methods only and cross validation by laboratory analogous experiments has not been conducted yet. To fill this gap we perform the first laboratory experiments of mantle convection driven by microwave-generated internal heating. We use a 30×30×5 cm3 experimental tank filled with 0.5 % Natrosol in water mixture (viscosity 0.6 Pa.s at 20°C). The fluid is heated from within by a microwave device that delivers a uniform volumetric heating from 10 to 70 kW/m3; the upper boundary of the fluid is kept at constant temperature, whereas the lower boundary is adiabatic. The velocity field is determined with particle image velocimetry and the temperature field is measured using thermochromic liquid crystals which enable us to charaterize the geometry of the convective regime as well as its bulk thermal evolution. Numerical simulations, conducted using Stag-3D in 3D cartesian geometry, reproduce the experimental setup (i.e., boundary conditions, box aspect ratio, temperature dependence of physical parameters, internal heating rate). The successful comparison between the experimental and numerical results validates our approach of modelling internal heating using microwaves.

  2. Microwave-based laboratory experiments for internally-heated mantle convection

    SciTech Connect

    Limare, A.; Di Giuseppe, E.; Vilella, K.; Farnetani, C. G.; Kaminski, E.; Jaupart, C.; Surducan, E.; Surducan, V.; Neamtu, C.

    2013-11-13

    The thermal evolution of terrestrial planets is mainly controlled by the amount of radioactive heat sources in their mantle, and by the geometry and efficiency of solid state thermo-chemical convection within. So far, these systems have been studied using numerical methods only and cross validation by laboratory analogous experiments has not been conducted yet. To fill this gap we perform the first laboratory experiments of mantle convection driven by microwave-generated internal heating. We use a 30×30×5 cm{sup 3} experimental tank filled with 0.5 % Natrosol in water mixture (viscosity 0.6 Pa.s at 20°C). The fluid is heated from within by a microwave device that delivers a uniform volumetric heating from 10 to 70 kW/m{sup 3}; the upper boundary of the fluid is kept at constant temperature, whereas the lower boundary is adiabatic. The velocity field is determined with particle image velocimetry and the temperature field is measured using thermochromic liquid crystals which enable us to charaterize the geometry of the convective regime as well as its bulk thermal evolution. Numerical simulations, conducted using Stag-3D in 3D cartesian geometry, reproduce the experimental setup (i.e., boundary conditions, box aspect ratio, temperature dependence of physical parameters, internal heating rate). The successful comparison between the experimental and numerical results validates our approach of modelling internal heating using microwaves.

  3. Combining Satellite Microwave Radiometer and Radar Observations to Estimate Atmospheric Latent Heating Profiles

    NASA Technical Reports Server (NTRS)

    Grecu, Mircea; Olson, William S.; Shie, Chung-Lin; L'Ecuyer, Tristan S.; Tao, Wei-Kuo

    2009-01-01

    In this study, satellite passive microwave sensor observations from the TRMM Microwave Imager (TMI) are utilized to make estimates of latent + eddy sensible heating rates (Q1-QR) in regions of precipitation. The TMI heating algorithm (TRAIN) is calibrated, or "trained" using relatively accurate estimates of heating based upon spaceborne Precipitation Radar (PR) observations collocated with the TMI observations over a one-month period. The heating estimation technique is based upon a previously described Bayesian methodology, but with improvements in supporting cloud-resolving model simulations, an adjustment of precipitation echo tops to compensate for model biases, and a separate scaling of convective and stratiform heating components that leads to an approximate balance between estimated vertically-integrated condensation and surface precipitation. Estimates of Q1-QR from TMI compare favorably with the PR training estimates and show only modest sensitivity to the cloud-resolving model simulations of heating used to construct the training data. Moreover, the net condensation in the corresponding annual mean satellite latent heating profile is within a few percent of the annual mean surface precipitation rate over the tropical and subtropical oceans where the algorithm is applied. Comparisons of Q1 produced by combining TMI Q1-QR with independently derived estimates of QR show reasonable agreement with rawinsonde-based analyses of Q1 from two field campaigns, although the satellite estimates exhibit heating profile structure with sharper and more intense heating peaks than the rawinsonde estimates. 2

  4. Metabolic effects of microwave radiation and convection heating on human mononuclear leukocytes

    SciTech Connect

    Kiel, J.L.; Wong, L.S.; Erwin, D.N.

    1986-01-01

    The effects of microwave radiation (2450 MHz, continuous wave, mean specific absorption rate of 103.5 +/- 4.2 W/kg) and convection heating on the nonphosphorylating oxidative metabolism of human peripheral mononuclear leukocytes (96% lymphocytes, 4% monocytes) at 37 degrees C were investigated. Metabolic activity, determined by chemiluminescence (CL) of cells challenged with luminol (5-amino-2,3-dihydro-1,4-phthalazinedione) linked to bovine serum albumin, was detected with a brightness photometer. A significant stimulation after microwave exposure (p less than 0.005) over total CL of matched 37 degrees C incubator controls was observed. A similar degree of stimulation compared to incubator controls was also detected after sham treatment. There was no significant difference between changes in total CL or stimulation indices of the microwave and sham exposed groups. It appears that exposure to microwave radiation, under normothermic (37 +/- 0.03 degrees C) conditions, has no effect on the oxidative metabolic activity of human peripheral mononuclear leukocytes. However, the significant differences between microwave or sham exposed cells and their respective incubator controls occurred because the temperature of the incubator controls did not exceed 35.9 degrees C and this temperature required 39 minutes to reach from 22 degrees C. Slow heating of incubator controls must be accounted for in thermal and radiofrequency radiation studies in vitro.

  5. Femtosecond filament initiated, microwave heated cavity-free nitrogen laser in air

    NASA Astrophysics Data System (ADS)

    Kartashov, Daniil; Shneider, Mikhail N.

    2017-03-01

    We present the results of numerical modeling of the igniter-heater concept for initiation of standoff, cavity free lasing action in the atmosphere when a femtosecond laser filament is used for plasma generation (igniter) and a microwave heater provides electron-collision pumping of electronic states in molecular nitrogen. By solving numerically the kinetic equation for the energy distribution function of electrons, generated in a femtosecond laser filament and heated by a microwave beam, we identify the conditions enabling single-pass, standoff UV-laser from molecular nitrogen in the atmosphere. The plasma density, the minimum amplitude of the microwave field, and the small-signal gain, necessary to achieve the lasing, are determined. We demonstrate that lasing build up time can be minimized and efficiency improved by using elliptically polarized laser pulses for filamentation. It is shown that realization of the filament-igniter, microwave-heater concept of the sky laser at low altitudes would require a microwave source of hundreds of kilowatt-megawatt power. The required microwave power can be reduced by several orders of magnitude when the igniter-heater scheme is used at the 10-30 km range of altitudes.

  6. Microwave Heating of Crystals with Gold Nanoparticles and Synovial Fluid under Synthetic Skin Patches

    PubMed Central

    2017-01-01

    Gout is a disease with elusive treatment options. Reduction of the size of l-alanine crystals as a model crystal for gouty tophi with the use of a monomode solid-state microwave was examined as a possible therapeutic aid. The effect of microwave heating on l-alanine crystals in the presence of gold nanoparticles (Au NPs) in solution and synovial fluid (SF) in a plastic pouch through a synthetic skin patch was investigated. In this regard, three experimental paradigms were employed: Paradigm 1 includes the effect of variable microwave power (5–10 W) and variable heating time (5–60 s) and Au NPs in water (20 nm size, volume of 10 μL) in a plastic pouch (1 × 2 cm2 in size). Paradigm 2 includes the effect of a variable volume of 20 nm Au NPs in a variable volume of SF up to 100 μL in a plastic pouch at a constant microwave power (10 W) for 30 s. Paradigm 3 includes the effect of constant microwave power (10 W) and microwave heating time (30 s), constant volume of Au NPs (100 μL), and variable size of Au NPs (20–200 nm) placed in a plastic pouch through a synthetic skin patch. In these experiments, an average of 60–100% reduction in the size of an l-alanine crystal (initial size = 450 μm) without damage to the synthetic skin or increasing the temperature of the samples beyond the physiological range was reported. PMID:28983527

  7. Microwave Heating of Crystals with Gold Nanoparticles and Synovial Fluid under Synthetic Skin Patches.

    PubMed

    McLemore, Gabrielle L; Toker, Salih; Boone-Kukoyi, Zainab; Ajifa, Hillary; Lansiquot, Carisse; Nwawulu, Chinenye; Onyedum, Stanley; Kioko, Bridgit M; Aslan, Kadir

    2017-09-30

    Gout is a disease with elusive treatment options. Reduction of the size of l-alanine crystals as a model crystal for gouty tophi with the use of a monomode solid-state microwave was examined as a possible therapeutic aid. The effect of microwave heating on l-alanine crystals in the presence of gold nanoparticles (Au NPs) in solution and synovial fluid (SF) in a plastic pouch through a synthetic skin patch was investigated. In this regard, three experimental paradigms were employed: Paradigm 1 includes the effect of variable microwave power (5-10 W) and variable heating time (5-60 s) and Au NPs in water (20 nm size, volume of 10 μL) in a plastic pouch (1 × 2 cm(2) in size). Paradigm 2 includes the effect of a variable volume of 20 nm Au NPs in a variable volume of SF up to 100 μL in a plastic pouch at a constant microwave power (10 W) for 30 s. Paradigm 3 includes the effect of constant microwave power (10 W) and microwave heating time (30 s), constant volume of Au NPs (100 μL), and variable size of Au NPs (20-200 nm) placed in a plastic pouch through a synthetic skin patch. In these experiments, an average of 60-100% reduction in the size of an l-alanine crystal (initial size = 450 μm) without damage to the synthetic skin or increasing the temperature of the samples beyond the physiological range was reported.

  8. An investigation of phase transformation of titania slag using microwave heating

    NASA Astrophysics Data System (ADS)

    Chen, Guo; Chen, Jin; Peng, Jinhui

    2016-09-01

    The influences of microwave heating on the phase transformation of titania slag were systematically investigated. The thermal stability, surface chemical functional groups and microstructure of the titania slag before and after microwave heating, at a temperature of 950 °C for 60 min, were also analyzed using thermogravimetry and differential thermal analysis (TG-DSC), Fourier transform infrared spectroscopy (FT-IR) spectrum and scanning electron microscope (SEM), respectively. The TG-DSC analysis revealed that the phase transformation of the titania slag from anatase TiO2 to rutile TiO2 occurred between 750 and 1000 °C. The FT-IR rustles demonstrate that the banding form of Ti4+, Ti3+ and Ti2+ ions and the methyl groups on the surface of the titania slag has changed and a new chemical bond Ti-OH was formed. The results of SEM showed that a large number of regulation rutile TiO2 crystals were found on the surface of the microwave-treated samples and the synthetic rutile has been synthesized successfully using microwave heating.

  9. Application of response surface methodology for optimization of parameters for microwave heating of rare earth carbonates

    NASA Astrophysics Data System (ADS)

    Yin, Shaohua; Lin, Guo; Li, Shiwei; Peng, Jinhui; Zhang, Libo

    2016-09-01

    Microwave heating has been applied in the field of drying rare earth carbonates to improve drying efficiency and reduce energy consumption. The effects of power density, material thickness and drying time on the weight reduction (WR) are studied using response surface methodology (RSM). The results show that RSM is feasible to describe the relationship between the independent variables and weight reduction. Based on the analysis of variance (ANOVA), the model is in accordance with the experimental data. The optimum experiment conditions are power density 6 w/g, material thickness 15 mm and drying time 15 min, resulting in an experimental weight reduction of 73%. Comparative experiments show that microwave drying has the advantages of rapid dehydration and energy conservation. Particle analysis shows that the size distribution of rare earth carbonates after microwave drying is more even than those in an oven. Based on these findings, microwave heating technology has an important meaning to energy-saving and improvement of production efficiency for rare earth smelting enterprises and is a green heating process.

  10. Preparation of high surface area activated carbon from coconut shells using microwave heating.

    PubMed

    Yang, Kunbin; Peng, Jinhui; Srinivasakannan, C; Zhang, Libo; Xia, Hongying; Duan, Xinhui

    2010-08-01

    The present study attempts to utilize coconut shell to prepare activated carbon using agents such as steam, CO(2) and a mixture of steam-CO(2) with microwave heating. Experimental results show that the BET surface area of activated carbons irrespective of the activation agent resulted in surface area in excess of 2000 m(2)/g. The activation time using microwave heating is very much shorter, while the yield of the activated carbon compares well with the conventional heating methods. The activated carbon prepared using CO(2) activation has the largest BET surface area, however the activation time is approximately 2.5 times higher than the activation using steam or mixture of steam-CO(2). The chemical structure of activated carbons examined using Fourier transformed infra-red spectra (FTIR) did not show any variation in the surface functional groups of the activated carbon prepared using different activation agents.

  11. Consequences of microwave heating and frying on the lipid fraction of chicken and beef patties.

    PubMed

    Echarte, M; Ansorena, Diana; Astiasarán, Iciar

    2003-09-24

    Two types of commercial meat patties were analyzed to evaluate the effect of two applied cooking methods on the lipid fraction and the cholesterol oxidation process during heating. Microwave heating hardly modified the fatty acid profiles of both chicken and beef patties, whereas frying in olive oil increased oleic and eicosapentaenoic acids and decreased linoleic and docosahexaenoic acids in both types of products. Frying improved the omega6/omega3 fatty acids ratio in beef patties from 10.67 (raw) to 5.37 (fried). Total cholesterol oxidation product (COP) increments were 5.3-6.1-fold with microwave heating and 1.5-2.6-fold with frying. Chicken patties, raw and cooked, had a COP content twice as high as the corresponding beef ones.

  12. Mixture for producing fracture-resistant, fiber-reinforced ceramic material by microwave heating

    DOEpatents

    Meek, Thomas T.; Blake, Rodger D.

    1987-01-01

    A fracture-resistant, fiber-reinforced ceramic substrate is produced by a method which involves preparing a ceramic precursor mixture comprising glass material, a coupling agent, and resilient fibers, and then exposing the mixture to microwave energy. The microwave field orients the fibers in the resulting ceramic material in a desired pattern wherein heat later generated in or on the substrate can be dissipated in a desired geometric pattern parallel to the fiber pattern. Additionally, the shunt capacitance of the fracture-resistant, fiber-reinforced ceramic substrate is lower which provides for a quicker transit time for electronic pulses in any conducting pathway etched into the ceramic substrate.

  13. The effect of wall losses in the numerical simulation of microwave heating problems.

    PubMed

    Ehlers, R A; Dibben, D C; Metaxas, A C

    2000-01-01

    A study is made into the numerical modeling of wall losses for a microwave heating application. It makes use of a surface integral term for both a frequency and time domain finite edge element formulation in order to model the wall impedance of the enclosed microwave cavity. The paper describes how the surface element matrix of the complex wall impedance is combined with the matrix formulation. The results are checked against analytical expressions for a single mode resonant cavity. An analysis on the effect of lossy walls is provided using four low-loss material insertions over a range of surface conductivities.

  14. Mixture for producing fracture-resistant, fiber-reinforced ceramic material by microwave heating

    DOEpatents

    Meek, T.T.; Blake, R.D.

    1987-09-22

    A fracture-resistant, fiber-reinforced ceramic substrate is produced by a method which involves preparing a ceramic precursor mixture comprising glass material, a coupling agent, and resilient fibers, and then exposing the mixture to microwave energy. The microwave field orients the fibers in the resulting ceramic material in a desired pattern wherein heat later generated in or on the substrate can be dissipated in a desired geometric pattern parallel to the fiber pattern. Additionally, the shunt capacitance of the fracture-resistant, fiber-reinforced ceramic substrate is lower which provides for a quicker transit time for electronic pulses in any conducting pathway etched into the ceramic substrate. 2 figs.

  15. Mixture for producing fracture-resistant, fiber-reinforced ceramic material by microwave heating

    DOEpatents

    Meek, T.T.; Blake, R.D.

    1985-04-03

    A fracture-resistant, fiber-reinforced ceramic substrate is produced by a method which involves preparing a ceramic precursor mixture comprising glass material, a coupling agent, and resilient fibers, and then exposing the mixture to microwave energy. The microwave field orients the fibers in the resulting ceramic material in a desired pattern wherein heat later generated in or on the substrate can be dissipated in a desired geometric pattern parallel to the fiber pattern. Additionally, the shunt capacitance of the fracture-resistant, fiber-reinforced ceramic substrate is lower which provides for a quicker transit time for electronic pulses in any conducting pathway etched into the ceramic substrate.

  16. Microwave heated reaction-bonded silicon nitride using an inverse temperature gradient

    NASA Astrophysics Data System (ADS)

    Fisher, J. G.; Bai, K.; Woo, S. K.; Han, I. S.; Lee, K. S.; Hong, K. S.; Seo, D. W.

    2003-04-01

    The nitridation behavior of Si under a microwave-heating source was studied. Si preforms were produced via an aqueous gel-casting route with 45 vol.% solids loading. Preforms up to 10 mm thick could be produced without cracking. Microwave nitridation of the Si preforms was carried out using a fiberboard insulation box without packing powders in order to cause an inverse temperature gradient. Nitridation began at the unusually low temperature of 950°C. Up to 74% nitridation was achieved by nitriding at 1120°C for 5 hr. Preforms displayed an inverse temperature gradient, with sintering and melting occurring in the center of the preforms.

  17. Heat and mass transport during microwave heating of mashed potato in domestic oven--model development, validation, and sensitivity analysis.

    PubMed

    Chen, Jiajia; Pitchai, Krishnamoorthy; Birla, Sohan; Negahban, Mehrdad; Jones, David; Subbiah, Jeyamkondan

    2014-10-01

    A 3-dimensional finite-element model coupling electromagnetics and heat and mass transfer was developed to understand the interactions between the microwaves and fresh mashed potato in a 500 mL tray. The model was validated by performing heating of mashed potato from 25 °C on a rotating turntable in a microwave oven, rated at 1200 W, for 3 min. The simulated spatial temperature profiles on the top and bottom layer of the mashed potato showed similar hot and cold spots when compared to the thermal images acquired by an infrared camera. Transient temperature profiles at 6 locations collected by fiber-optic sensors showed good agreement with predicted results, with the root mean square error ranging from 1.6 to 11.7 °C. The predicted total moisture loss matched well with the observed result. Several input parameters, such as the evaporation rate constant, the intrinsic permeability of water and gas, and the diffusion coefficient of water and gas, are not readily available for mashed potato, and they cannot be easily measured experimentally. Reported values for raw potato were used as baseline values. A sensitivity analysis of these input parameters on the temperature profiles and the total moisture loss was evaluated by changing the baseline values to their 10% and 1000%. The sensitivity analysis showed that the gas diffusion coefficient, intrinsic water permeability, and the evaporation rate constant greatly influenced the predicted temperature and total moisture loss, while the intrinsic gas permeability and the water diffusion coefficient had little influence. This model can be used by the food product developers to understand microwave heating of food products spatially and temporally. This tool will allow food product developers to design food package systems that would heat more uniformly in various microwave ovens. The sensitivity analysis of this study will help us determine the most significant parameters that need to be measured accurately for reliable

  18. Effects of anomalous permittivity on the microwave heating of zinc oxide

    NASA Astrophysics Data System (ADS)

    Martin, L. P.; Dadon, D.; Rosen, M.; Gershon, D.; Rybakov, K. I.; Birman, A.; Calame, J. P.; Levush, B.; Carmel, Y.; Hutcheon, R.

    1998-01-01

    Highly nonuniform heating has been observed in zinc oxide (ZnO) powder compacts exposed to 2.45 GHz microwaves in oxygen deficient atmospheres such as pure nitrogen or argon. This phenomenon manifests as a localized zone of rapid heating which propagates outward from the sample core, and is documented by real-time surface and core temperature measurements performed during the microwave exposure. Measurements of the complex permittivity, ɛ″, during heating of identical ZnO samples in a conventional furnace and in a nitrogen atmosphere, demonstrated that ɛ″ experiences at least one significant maximum between 200 and 500 °C. Mass spectrometry results indicate that the peaks in ɛ″ correlate well with the rate of desorption of chemisorbed water from the surface of the ZnO powder. It was also noted that the nonuniform heating does not manifest when the microwave exposure is performed in air. Similarly, the anomalous peaks in ɛ″ are almost completely suppressed during heating in air. It is well known that oxygen adsorbs strongly to the surface of ZnO in the temperature range from room temperature to 300 °C, and that this adsorption results in a drastic decrease in the electrical conductivity and, thus, in ɛ″. It is proposed, therefore, that the effect of water desorption upon the complex permittivity may be, in effect, counterbalanced by the adsorption oxygen from the atmosphere. The effect of this behavior may be significant during microwave processing, where nonuniform power absorption can result in extremely localized heating.

  19. Thermal oxidation of rice bran oil during oven test and microwave heating.

    PubMed

    Mishra, Richa; Sharma, Harish K; Sarkar, Bhavesh C; Singh, Charanjiv

    2012-04-01

    The purpose of the present study was to evaluate the oxidative stability of physically refined rice bran oil (RBO) under oven heating at 63 °C and microwave heating conditions by absorptivity. Oil samples with tertiary-butylhydroquinone (TBHQ) (100 ppm and 200 ppm), citric acid (CA), butylhydroxyanisole/butylhydroxytoluene (BHA/BHT) and in other combination, BHA/BHT+CA were submitted to oven test for 6 days, and the linear coefficient of correlation between peroxide value and absorptivity at 232 nm was determined. The gradual increase in peroxide value and absorptivity at 232 nm was observed in all the RBO samples, control and antioxidant added. RBO samples added with tertiary-butylhydroquinone (TBHQ) had shown the least peroxide value and absorptivity as 6.10 and 5.8 respectively, when added at a concentration of 200 ppm whereas; the control RBO samples had shown the maximum values. The peroxide values obtained from the correlations during the oven test were found closely correlated with the peroxide values obtained during the microwave oven heating experimentally. The effect of microwave heating on the oryzanol content and p-anisidine value was also observed and the correlation to the oven test was established. The oryzanol content and p-anisidine values obtained after oven heating when correlated to the microwave heating data showed the oryzanol content 13,371, 13,267 and 13,188 ppm after 1 day, 4 days and 5 days respectively which were closely correlated with the experimental value.

  20. Effect of the load size on the efficiency of microwave heating under stop flow and continuous flow conditions.

    PubMed

    Patil, Narendra G; Rebrov, Evgeny V; Eränen, Kari; Benaskar, Faysal; Meuldijk, Jan; Mikkola, Jyri-Pekka; Hessel, Volker; Hulshof, Lumbertus A; Murzin, Dmitry Yu; Schouten, Jaap C

    2012-01-01

    A novel heating efficiency analysis of the microwave heated stop-flow (i.e. stagnant liquid) and continuous-flow reactors has been presented. The thermal losses to the surrounding air by natural convection have been taken into account for heating efficiency calculation of the microwave heating process. The effect of the load diameter in the range of 4-29 mm on the heating efficiency of ethylene glycol was studied in a single mode microwave cavity under continuous flow and stop-flow conditions. The variation of the microwave absorbing properties of the load with temperature was estimated. Under stop-flow conditions, the heating efficiency depends on the load diameter. The highest heating efficiency has been observed at the load diameter close to the half wavelength of the electromagnetic field in the corresponding medium. Under continuous-flow conditions, the heating efficiency increased linearly. However, microwave leakage above the propagation diameter restricted further experimentation at higher load diameters. Contrary to the stop-flow conditions, the load temperature did not raise monotonously from the inlet to outlet under continuous-flow conditions. This was due to the combined effect of lagging convective heat fluxes in comparison to volumetric heating. This severely disturbs the uniformity of the electromagnetic field in the axial direction and creates areas of high and low field intensity along the load Length decreasing the heating efficiency as compared to stop-flow conditions.

  1. A new osteonecrosis animal model of the femoral head induced by microwave heating and repaired with tissue engineered bone

    PubMed Central

    Han, Rui; Geng, Chengkui; Wang, Yongnian; Wei, Lei

    2008-01-01

    The objective of this research was to induce a new animal model of osteonecrosis of the femoral head (ONFH) by microwave heating and then repair with tissue engineered bone. The bilateral femoral heads of 84 rabbits were heated by microwave at various temperatures. Tissue engineered bone was used to repair the osteonecrosis of femoral heads induced by microwave heating. The roentgenographic and histological examinations were used to evaluate the results. The femoral heads heated at 55°C for ten minutes showed low density and cystic changes in X-ray photographs, osteonecrosis and repair occurred simultaneously in histology at four and eight weeks, and 69% femoral heads collapsed at 12 weeks. The ability of tissue engineered bone to repair the osteonecrosis was close to that of cancellous bone autograft. The new animal model of ONFH could be induced by microwave heating, and the tissue engineering technique will provide an effective treatment. PMID:18956184

  2. Influence of Microwave Heating and Thermal Auxiliary on Decomposition of Siderite

    NASA Astrophysics Data System (ADS)

    Celikdemir, Mehmet; Sarikaya, Musa; Depci, Tolga; Aydogmus, Ramazan

    2016-10-01

    In the present study, microwave radiation was used to decrease power inputs and roasting duration time for thermal decomposition of Deveci, Hekimhan siderite ore. The siderite was not enough to absorb adequate microwave radiation to start the decomposition or roasting reaction. Therefore, sucrose as a thermal auxiliary was added to the raw siderite ore before microwave irradiation. The effect of amount of sucrose (10 to 30% by weight) against the duration of heating and roasting temperature of the thermal decomposition of siderite was investigated in the present study. On the contrary of the literature, the experimental results showed that the siderite was decomposed in 3 minutes with addition of 30 wt% sucrose and transformed to Fe3O4. The temperature, the weight loss and the magnetic susceptibility of the roasted final product were recorded as 1100 °C, 32.14 wt.% and 15410.03*10-8 m3/kg., respectively.

  3. Combined microwave heating and surface cooling of the cornea.

    PubMed

    Trembly, B S; Keates, R H

    1991-01-01

    We investigated a nonsurgical means of reshaping the cornea to correct hyperopia, keratoconus, or myopia. The object was to heat the central stroma of the cornea to the shrinkage temperature of collagen, 55-58 degrees C. The heating device was an open-ended, coaxial, near-field applicator driven at 2450 MHz; it incorporates cooling of the cornea surface by flow of saline. We investigated the system theoretically by computing the 2-D, axisymmetric temperature distribution with the finite element method. We investigated the system experimentally by heating excised steer corneas. Histology showed the system could shrink the stroma to a depth of 0.6 mm while sparing the epithelium in 75% of cases; the diameter of shrinkage was 1.3 mm. Theory predicted a significantly deeper and narrower region of shrinkage than was observed.

  4. Evaluation of microwave oven heating for prediction of drug-excipient compatibilities and accelerated stability studies.

    PubMed

    Schou-Pedersen, Anne Marie V; Østergaard, Jesper; Cornett, Claus; Hansen, Steen Honoré

    2015-05-15

    Microwave ovens have been used extensively in organic synthesis in order to accelerate reaction rates. Here, a set up comprising a microwave oven combined with silicon carbide (SiC) plates for the controlled microwave heating of model formulations has been applied in order to investigate, if a microwave oven is applicable for accelerated drug stability testing. Chemical interactions were investigated in three selected model formulations of drug and excipients regarding the formation of ester and amide reaction products. In the accelerated stability studies, a design of experiments (DoE) approach was applied in order to be able to rank excipients regarding reactivity: Study A: cetirizine with PEG 400, sorbitol, glycerol and propylene glycol. Study B: 6-aminocaproic acid with citrate, acetate, tartrate and gluconate. Study C: atenolol with citric, tartaric, malic, glutaric, and sorbic acid. The model formulations were representative for oral solutions (co-solvents), parenteral solutions (buffer species) and solid dosage forms (organic acids applicable for solubility enhancement). The DoE studies showed overall that the same impurities were generated by microwave oven heating leading to temperatures between 150°C and 180°C as compared to accelerated stability studies performed at 40°C and 80°C using a conventional oven. Ranking of the reactivity of the excipients could be made in the DoE studies performed at 150-180°C, which was representative for the ranking obtained after storage at 40°C and 80°C. It was possible to reduce the time needed for drug-excipient compatibility testing of the three model formulations from weeks to less than an hour in the three case studies. The microwave oven is therefore considered to be an interesting alternative to conventional thermal techniques for the investigation of drug-excipient interactions during preformulation. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Accelerated Amidization of Branched Poly(ethylenimine)/Poly(acrylic acid) Multilayer Films by Microwave Heating.

    PubMed

    Lin, Kehua; Gu, Yuanqing; Zhang, Huan; Qiang, Zhe; Vogt, Bryan D; Zacharia, Nicole S

    2016-09-13

    Chemical cross-linking of layer-by-layer assembled films promotes mechanical stability and robustness in a wide variety of environments, which can be a challenge for polyelectrolyte multilayers in saline environments or for multilayers made from weak polyelectrolytes in environments with extreme pHs. Heating branched poly(ethylenimine)/poly(acrylic acid) (BPEI/PAA) multilayers at sufficiently high temperatures drives amidization and dehydration to covalently cross-link the film, but this reaction is rather slow, typically requiring heating for hours for appreciable cross-linking to occur. Here, a more than one order of magnitude increase in the amidization kinetics is realized through microwave heating of BPEI/PAA multilayers on indium tin oxide (ITO)/glass substrates. The cross-linking reaction is tracked using infrared spectroscopic ellipsometry to monitor the development of the cross-linking products. For thick films (∼1500 nm), gradients in cross-link density can be readily identified by infrared ellipsometry. Such gradients in cross-link density are driven by the temperature gradient developed by the localized heating of ITO by microwaves. This significant acceleration of reactions using microwaves to generate a well-defined cross-link network as well as being a simple method for developing graded materials should open new applications for these polymer films and coatings.

  6. Microwave furnace having microwave compatible dilatometer

    DOEpatents

    Kimrey, Jr., Harold D.; Janney, Mark A.; Ferber, Mattison K.

    1992-01-01

    An apparatus for measuring and monitoring a change in the dimension of a sample being heated by microwave energy is described. The apparatus comprises a microwave heating device for heating a sample by microwave energy, a microwave compatible dilatometer for measuring and monitoring a change in the dimension of the sample being heated by microwave energy without leaking microwaves out of the microwave heating device, and a temperature determination device for measuring and monitoring the temperature of the sample being heated by microwave energy.

  7. Microwave furnace having microwave compatible dilatometer

    DOEpatents

    Kimrey, H.D. Jr.; Janney, M.A.; Ferber, M.K.

    1992-03-24

    An apparatus for measuring and monitoring a change in the dimension of a sample being heated by microwave energy is described. The apparatus comprises a microwave heating device for heating a sample by microwave energy, a microwave compatible dilatometer for measuring and monitoring a change in the dimension of the sample being heated by microwave energy without leaking microwaves out of the microwave heating device, and a temperature determination device for measuring and monitoring the temperature of the sample being heated by microwave energy. 2 figs.

  8. Processed Meat Protein and Heat-Stable Peptide Marker Identification Using Microwave-Assisted Tryptic Digestion.

    PubMed

    Montowska, Magdalena; Pospiech, Edward

    2016-12-01

    New approaches to rapid examination of proteins and peptides in complex food matrices are of great interest to the community of food scientists. The aim of the study is to examine the influence of microwave irradiation on the acceleration of enzymatic cleavage and enzymatic digestion of denatured proteins in cooked meat of five species (cattle, horse, pig, chicken and turkey) and processed meat products (coarsely minced, smoked, cooked and semi-dried sausages). Severe protein aggregation occurred not only in heated meat under harsh treatment at 190 °C but also in processed meat products. All the protein aggregates were thoroughly hydrolyzed after 1 h of trypsin treatment with short exposure times of 40 and 20 s to microwave irradiation at 138 and 303 W. There were much more missed cleavage sites observed in all microwave-assisted digestions. Despite the incompleteness of microwave-assisted digestion, six unique peptide markers were detected, which allowed unambiguous identification of processed meat derived from the examined species. Although the microwave-assisted tryptic digestion can serve as a tool for rapid and high-throughput protein identification, great caution and pre-evaluation of individual samples is recommended in protein quantitation.

  9. Processed Meat Protein and Heat-Stable Peptide Marker Identification Using Microwave-Assisted Tryptic Digestion

    PubMed Central

    Pospiech, Edward

    2016-01-01

    Summary New approaches to rapid examination of proteins and peptides in complex food matrices are of great interest to the community of food scientists. The aim of the study is to examine the influence of microwave irradiation on the acceleration of enzymatic cleavage and enzymatic digestion of denatured proteins in cooked meat of five species (cattle, horse, pig, chicken and turkey) and processed meat products (coarsely minced, smoked, cooked and semi-dried sausages). Severe protein aggregation occurred not only in heated meat under harsh treatment at 190 °C but also in processed meat products. All the protein aggregates were thoroughly hydrolyzed after 1 h of trypsin treatment with short exposure times of 40 and 20 s to microwave irradiation at 138 and 303 W. There were much more missed cleavage sites observed in all microwave-assisted digestions. Despite the incompleteness of microwave-assisted digestion, six unique peptide markers were detected, which allowed unambiguous identification of processed meat derived from the examined species. Although the microwave-assisted tryptic digestion can serve as a tool for rapid and high-throughput protein identification, great caution and pre-evaluation of individual samples is recommended in protein quantitation. PMID:28115907

  10. An experimental study of waveguide coupled microwave heating with conventional multicusp negative ion sources

    SciTech Connect

    Komppula, J.; Kalvas, T.; Koivisto, H.; Laulainen, J.; Tarvainen, O.

    2015-04-08

    Negative ion production with conventional multicusp plasma chambers utilizing 2.45 GHz microwave heating is demonstrated. The experimental results were obtained with the multicusp plasma chambers and extraction systems of the RF-driven RADIS ion source and the filament driven arc discharge ion source LIISA. A waveguide microwave coupling system, which is almost similar to the one used with the SILHI ion source, was used. The results demonstrate that at least one third of negative ion beam obtained with inductive RF-coupling (RADIS) or arc discharge (LIISA) can be achieved with 1 kW of 2.45 GHz microwave power in CW mode without any modification of the plasma chamber. The co-extracted electron to H{sup −} ratio and the optimum pressure range were observed to be similar for both heating methods. The behaviour of the plasma implies that the energy transfer from the microwaves to the plasma electrons is mainly an off-resonance process.

  11. Galvanic Corrosion Behavior of Microwave Welded and Post-weld Heat-Treated Inconel-718 Joints

    NASA Astrophysics Data System (ADS)

    Bansal, Amit; Sharma, Apurbba Kumar; Kumar, Pradeep

    2017-05-01

    In the present study, corrosion behavior of microwave welded Inconel-718 at various conditions was investigated. Welding of Inconel-718 in 980 °C solution-treated condition was performed using microwave hybrid heating technique. The microwave welds were subjected to post-heat treatment for improving its microstructure and mechanical properties by solubilizing the Nb-enriched Laves phase. The microstructural features of the fabricated welds at various conditions were investigated through scanning electron microscopy. The electrochemical testing results revealed that Inconel-718 welds were galvanic corroded when they were anodically polarized in 3.5 wt.% NaCl solution at 28 °C. The difference in the corrosion potentials between the base metal (BM) and fusion zone (FZ) in an Inconel-718 weld was the main factor for galvanic corrosion. The highest corrosion was occurred in the as-welded/aged weldments, followed by 980 °C solution-treated and aged weldments, as-welded specimen, and 1080 °C solution-treated and aged (1080STA) weldments. The least galvanic corrosion was occurred in the 1080STA specimens due to almost uniform microstructure developed in the weldment after the treatment. Thus, it was possible to minimize the galvanic corrosion in the microwave welded Inconel-718 by 1080STA treatment which resulted in reducing the difference in corrosion potentials between the BM and the FZ.

  12. Nitrogen-Doped Carbon Fiber Paper by Active Screen Plasma Nitriding and Its Microwave Heating Properties.

    PubMed

    Zhu, Naishu; Ma, Shining; Sun, Xiaofeng

    2016-12-28

    In this paper, active screen plasma nitriding (ASPN) treatment was performed on polyacrylonitrile carbon fiber papers. Electric resistivity and microwave loss factor of carbon fiber were described to establish the relationship between processing parameters and fiber's ability to absorb microwaves. The surface processing effect of carbon fiber could be characterized by dynamic thermal mechanical analyzer testing on composites made of carbon fiber. When the process temperature was at 175 °C, it was conducive to obtaining good performance of dynamical mechanical properties. The treatment provided a way to change microwave heating properties of carbon fiber paper by performing different treatment conditions, such as temperature and time parameters. Atomic force microscope, scanning electron microscope, and X-ray photoelectron spectroscopy analysis showed that, during the course of ASPN treatment on carbon fiber paper, nitrogen group was introduced and silicon group was removed. The treatment of nitrogen-doped carbon fiber paper represented an alternative promising candidate for microwave curing materials used in repairing and heating technology, furthermore, an efficient dielectric layer material for radar-absorbing structure composite in metamaterial technology.

  13. Using a conformal water bolus to adjust heating patterns of microwave waveguide applicators

    NASA Astrophysics Data System (ADS)

    Stauffer, Paul R.; Rodrigues, Dario B.; Sinahon, Randolf; Sbarro, Lyndsey; Beckhoff, Valeria; Hurwitz, Mark D.

    2017-02-01

    Background: Hyperthermia, i.e., raising tissue temperature to 40-45°C for 60 min, has been demonstrated to increase the effectiveness of radiation and chemotherapy for cancer. Although multi-element conformal heat applicators are under development to provide more adjustable heating of contoured anatomy, to date the most often used applicator to heat superficial disease is the simple microwave waveguide. With only a single power input, the operator must be resourceful to adjust heat treatment to accommodate variable size and shape tumors spreading across contoured anatomy. Methods: We used multiphysics simulation software that couples electromagnetic, thermal and fluid dynamics physics to simulate heating patterns in superficial tumors from commercially available microwave waveguide applicators. Temperature distributions were calculated inside homogenous muscle and layered skin-fat-muscle-tumor-bone tissue loads for a typical range of applicator coupling configurations and size of waterbolus. Variable thickness waterbolus was simulated as necessary to accommodate contoured anatomy. Physical models of several treatment configurations were constructed for comparison of simulation results with experimental specific absorption rate (SAR) measurements in homogenous muscle phantom. Results: Accuracy of the simulation model was confirmed with experimental SAR measurements of three unique applicator setups. Simulations demonstrated the ability to generate a wide range of power deposition patterns with commercially available waveguide antennas by controllably varying size and thickness of the waterbolus layer. Conclusion: Heating characteristics of 915 MHz waveguide antennas can be varied over a wide range by controlled adjustment of microwave power, coupling configuration, and waterbolus lateral size and thickness. The uniformity of thermal dose delivered to superficial tumors can be improved by cyclic switching of waterbolus thickness during treatment to proactively shift

  14. Effects of shape and size of agar gels on heating uniformity during pulsed microwave treatment.

    PubMed

    Soto-Reyes, Nohemí; Temis-Pérez, Ana L; López-Malo, Aurelio; Rojas-Laguna, Roberto; Sosa-Morales, María Elena

    2015-05-01

    Model gel systems with different shape (sphere, cylinder, and slab) and size (180 and 290 g) were prepared with agar (5%) and sucrose (5%). Dielectric constant (ε'), loss factor (ε"), thermophysical properties, and temperature distribution of the model system were measured. Each agar model system was immersed and suspended in water, and then, heated in a microwave oven with intermittent heating until the core temperature reached 50 °C. The ε' and ε" of agar gels decreased when frequency increased. The density and thermal conductivity values of the agar gels were 1033 kg/m(3) and 0.55 W/m °C, respectively. The temperature distribution of sphere, cylinder, and slab was different when similar power doses were applied. The slab reached 50 °C in less time (10 min) and showed a more uniform heating than spheres and cylinders in both sizes. Agar model systems of 180 g heated faster than those of 290 g. The coldest point was the center of the model systems in all studied cases. Shape and size are critical food factors that affect the heating uniformity during microwave heating processes.

  15. Infrared Fiber Radiometer For Thermometry In Therapeutic Microwave And Radio Frequency Heating

    NASA Astrophysics Data System (ADS)

    Katzir, A.; Bowman, F.; Narciso, H.; Asfour, Y.; Zur, A.

    1987-04-01

    Hyperthermia in cancer treatment involves heating malignant tumors to 42.5-43.0°C for an extended period (e.g. 30 min) in an attempt to obtain remission. For superficial and some deep seated tumors electromagnetic (microwave or radio frequency) field induced heating is often used. One of the severe problems with this therapeutic modality is the accurate measurement of temperature in the presence of a strong electromagnetic field. We have under development an infrared fiber-radiometer system which quantifies temperatures by measuring black body emission from the surface. This radiometer is based on a non-metallic, infrared fiber probe, which can operate either in contact or in non contact modes. When the fibers are incorporated in endoscopic catheters, internal body temperatures may be measured at those sites accessible via body orifices. In preliminary investigations the radiometer worked well in a strong microwave field, with an accuracy of ±0.5°C.

  16. Deposition of Hard Chrome Coating onto Heat Susceptible Substrates by Low Power Microwave Plasma Spray

    NASA Astrophysics Data System (ADS)

    Redza, Ahmad; Yasui, Toshiaki; Fukumoto, Masahiro

    2016-02-01

    Microwave plasma spray requires relatively low power, which is lower than 1 kW in comparison to other plasma spraying method. Until now, we are able to deposit Cu and Hydroxyapatite coating onto heat susceptible substrate, CFRP which are difficult for conventional plasma spray due to the excessive heat input. In this paper, a hard chromium coating was deposited onto SUS304 and CFRP by a low power microwave plasma spray technique. By controlling the working gas flow rate and spraying distance, a hard chrome coating with thickness of approximately 30 μm was successfully deposited onto CFRP substrate with hardness of 1110 Hv0.05. Furthermore, the coating produced here is higher than that produced by hard chrome plating.

  17. Combined Microwave and Sferics Measurements as a Continuous Proxy for Latent Heating in Mesoscale Model Predictions

    NASA Technical Reports Server (NTRS)

    Chang, D. -E.; Morales, C. A.; Weinman, J. A.; Olson, W. S.

    1999-01-01

    Planar rainfall distributions were retrieved from data provided by the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and Special Sensor Microwave Imager (SSM/I) radiometers. Lightning generates Very Low Frequency (VLF) radio noise pulses called sferics. Those pulses propagate over large distances so that they can be continuously monitored with a network of ground based radio receivers. An empirical relationship between the sferics rate and the convective rainfall permitted maps of convective latent heating profiles to be derived continuously from the sferics distributions. Those inferred latent heating rates were assimilated into the Penn State/NCAR Mesoscale Model (MM5) that depicted an intense winter cyclone that passed over Florida on 2 February 1998. When compared to a 14 hour MM5 rainfall forecast using conventional data, the use of lightning data improved the forecast.

  18. Combined Microwave and Sferics Measurements as a Continuous Proxy for Latent Heating in Mesoscale Model Predictions

    NASA Technical Reports Server (NTRS)

    Chang, D.-E.; Morales, C. A.; Weinman, J. A.; Olson, W. S.

    1999-01-01

    Planar rainfall distributions were retrieved from data provided by the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and Special Sensor Microwave/Imager (SSM/I) radiometers. Lightning generates Very Low Frequency (VLF) radio noise pulses called sferics. Those pulses propagate over large distances so that they can be continuously monitored with a network of ground based radio receivers. An empirical relationship between the sferics rate and the convective rainfall permitted maps of convective latent heating profiles to be derived continuously from the sferics distributions. Those inferred latent heating rates were assimilated into the Penn State/NCAR Mesoscale Model (MM5) that depicted an intense winter cyclone that passed over Florida on 2 February 1998. When compared to a 14 hour MM5 rainfall forecast using conventional data, the use of lightning data improved the forecast.

  19. Characterization of bulk stainless steel joints developed through microwave hybrid heating

    SciTech Connect

    Bansal, Amit; Sharma, Apurbba Kumar; Kumar, Pradeep; Das, Shantanu

    2014-05-01

    Processing of metallic materials through microwave heating is a challenging area of research. In the present work, joining of stainless steel-316 to stainless steel-316 in the bulk form has been carried out by placing stainless steel-316 powder at the interface and through targeted heating using microwave hybrid heating. The trials were carried out in a multimode microwave applicator at a frequency of 2.45 GHz and power 900 W. The developed joints were characterized using X-ray diffraction, field emission scanning electron microscopy equipped with energy dispersive X-ray spectroscope and measurement of Vicker's microhardness, porosity and tensile strength. The X-ray diffraction spectrum of the developed joint shows the presence of chromium carbide, iron carbide and iron silicide phases that eventually contribute to enhancement of the microhardness of the joint. The scanning electron microscope micrographs confirm classical metallurgical bonding between the substrate and the interface (molten powder) layer; the epitaxial growth rate was observed adjacent to the fusion zone. The average observed Vicker's microhardness in the joint zone on the grain boundary was significantly higher than that inside the grains due to the presence of various hard phases at the grain boundaries. Evaluation of the tensile strength of the joints showed an average ultimate tensile strength of 425.0 MPa with an average elongation of 9.44%. - Highlights: • Joining of stainless steel (SS-316) plates using microwave hybrid heating • Epitaxial growth rate observed adjacent to the fusion zone of welded joint • The ultimate tensile strength of the order of 425.0 MPa with 9.44% elongation.

  20. Cardiorespiratory Changes During Microwave-Induced Lethal Heat Stress and Beta-adrenergic Blockade

    DTIC Science & Technology

    1994-01-01

    ceptor blockade on thermoregulatory responses to envi- THz mimfARY AND CIVILAN use of microwave radiation ronmental heat exposure (or to exercise ...labetalol, a combined a- and/t- adrenoreceptor blocking drug. Br. low breathing in guinea pigs (38). Acute administration J. Clin. Pharmacol. 3, Suppl. 3: 681...AppL PhysioL 43: 292-296, 1977. tor antagonism in exercising men. The effects of pro- 5. Cabanac, M. Temperature regulation. Annu. Rev. PhysioL 38: o

  1. Microwave Heating of Synthetic Skin Samples for Potential Treatment of Gout Using the Metal-Assisted and Microwave-Accelerated Decrystallization Technique

    PubMed Central

    2016-01-01

    Physical stability of synthetic skin samples during their exposure to microwave heating was investigated to demonstrate the use of the metal-assisted and microwave-accelerated decrystallization (MAMAD) technique for potential biomedical applications. In this regard, optical microscopy and temperature measurements were employed for the qualitative and quantitative assessment of damage to synthetic skin samples during 20 s intermittent microwave heating using a monomode microwave source (at 8 GHz, 2–20 W) up to 120 s. The extent of damage to synthetic skin samples, assessed by the change in the surface area of skin samples, was negligible for microwave power of ≤7 W and more extensive damage (>50%) to skin samples occurred when exposed to >7 W at initial temperature range of 20–39 °C. The initial temperature of synthetic skin samples significantly affected the extent of change in temperature of synthetic skin samples during their exposure to microwave heating. The proof of principle use of the MAMAD technique was demonstrated for the decrystallization of a model biological crystal (l-alanine) placed under synthetic skin samples in the presence of gold nanoparticles. Our results showed that the size (initial size ∼850 μm) of l-alanine crystals can be reduced up to 60% in 120 s without damage to synthetic skin samples using the MAMAD technique. Finite-difference time-domain-based simulations of the electric field distribution of an 8 GHz monomode microwave radiation showed that synthetic skin samples are predicted to absorb ∼92.2% of the microwave radiation. PMID:27917407

  2. Microwave Heating of Synthetic Skin Samples for Potential Treatment of Gout Using the Metal-Assisted and Microwave-Accelerated Decrystallization Technique.

    PubMed

    Toker, Salih; Boone-Kukoyi, Zainab; Thompson, Nishone; Ajifa, Hillary; Clement, Travis; Ozturk, Birol; Aslan, Kadir

    2016-11-30

    Physical stability of synthetic skin samples during their exposure to microwave heating was investigated to demonstrate the use of the metal-assisted and microwave-accelerated decrystallization (MAMAD) technique for potential biomedical applications. In this regard, optical microscopy and temperature measurements were employed for the qualitative and quantitative assessment of damage to synthetic skin samples during 20 s intermittent microwave heating using a monomode microwave source (at 8 GHz, 2-20 W) up to 120 s. The extent of damage to synthetic skin samples, assessed by the change in the surface area of skin samples, was negligible for microwave power of ≤7 W and more extensive damage (>50%) to skin samples occurred when exposed to >7 W at initial temperature range of 20-39 °C. The initial temperature of synthetic skin samples significantly affected the extent of change in temperature of synthetic skin samples during their exposure to microwave heating. The proof of principle use of the MAMAD technique was demonstrated for the decrystallization of a model biological crystal (l-alanine) placed under synthetic skin samples in the presence of gold nanoparticles. Our results showed that the size (initial size ∼850 μm) of l-alanine crystals can be reduced up to 60% in 120 s without damage to synthetic skin samples using the MAMAD technique. Finite-difference time-domain-based simulations of the electric field distribution of an 8 GHz monomode microwave radiation showed that synthetic skin samples are predicted to absorb ∼92.2% of the microwave radiation.

  3. Optimizing electro-thermo Helds for soot oxidation using microwave heating and metal

    NASA Astrophysics Data System (ADS)

    Al-Wakeel, Haitham B.; Karim, Z. A. Abdul; Al-Kayiem, Hussain H.

    2015-04-01

    Soot is produced by incomplete combustion of various carbon-containing compounds. Soot is one of the main environmental pollutants and has become an important environmental and specific objective. To reduce soot from exhaust emission of diesel engine, a new technique is proposed and implemented by using metal inserted in the soot exposed to electromagnetic radiation. This paper presents a simulation to obtain optimum metal length and shape that give optimum electric field for attaining temperature enough for soot oxidation using microwave heating and a thin metal rod. Four cases were numerically examined to investigate the electric field and temperature distributions in a mono-mode TE10 microwave cavity having closed surfaces of perfect electric conductors. The operating frequency is 2.45 GHz, and power supply is 1500 W. The simulation methodology is coupling the absorbed electromagnetic energy with heat transfer energy. The absorbed electromagnetic energy is found from the electric field within the soot. The simulation was run using ANSYS based on finite element method. The results of the four simulation cases show that the optimum simulation is represented by case 2 where the value of electric field is 39000 V/m and heating time to arrive at the oxidation temperature (873 K) is 35 s using cylindrical metal rod of 8 mm length. It is revealed that the concept of achieving high temperature for soot oxidation by using thin metal rod inside a microwave cavity can be applied.

  4. Surface modification of plasmonic nanostructured materials with thiolated oligonucleotides in 10 seconds using selective microwave heating

    PubMed Central

    Abel, Biebele; Aslan, Kadir

    2013-01-01

    This study demonstrates the proof-of-principle of rapid surface modification of plasmonic nanostructured materials with oligonucleotides using low power microwave heating. Due to their interesting optical and electronic properties, silver nanoparticle films (SNFs, 2 nm thick) deposited onto glass slides were used as the model plasmonic nanostructured materials. Rapid surface modification of SNFs with oligonucleotides was carried out using two strategies (1) Strategy 1: for ss-oligonucleotides, surface hybridization and (2) Strategy 2: for ds-oligonucleotides, solution hybridization), where the samples were exposed to 10, 15, 30 and 60 seconds microwave heating. To assess the efficacy of our new rapid surface modification technique, identical experiments carried out without the microwave heating (i.e., conventional method), which requires 24 hours for the completion of the identical steps. It was found that SNFs can be modified with ss- and ds-oligonucleotides in 10 seconds, which typically requires several hours of incubation time for the chemisorption of thiol groups on to the planar metal surface using conventional techniques. PMID:23645933

  5. Simulations of microwave electron heating on field-reversed configuration driven by rotating magnetic field

    NASA Astrophysics Data System (ADS)

    Yang, Xiaokang; Petrov, Yuri; Koehn, Alf; Cohen, Sam; Ceccherini, Francesco; Galeotti, Laura; Dettrick, Sean; Binderbauer, Michl

    2016-10-01

    The rotating magnetic field-driven field-reversed configuration (FRC), such as Rotamak or PFRC experiment, was recently proposed as a test bench at Tri Alpha Energy to experimentally pioneer the study of microwave electron heating. In order to provide guidelines to the choice of microwave frequency and antenna position, as well as the desired target plasma profile, extensive simulations have been conducted with use of the GENRAY-C ray-tracing code for a wide range of frequencies from smaller than fundamental electron cyclotron resonant (ECR) frequency up to more than 30 harmonics of ECR. Based on the operational parameters of Rotamak plasma, simulations indicate that microwaves at a frequency around 10 GHz can heat electrons inside the separatrix layer. The physics of heating mechanism is similar for both the Rotamak and the C-2U FRC plasma, meaning that the magnitude of magnetic field goes down along the direction of ray propagation, therefore the rays, after the O-X-B mode conversion, encounter a basin of high harmonic EC resonances and mostly damp the power in the vicinity of the upper-hybrid resonance layer Detailed simulation results and plans for a future test bench will be presented.

  6. Effect of Heat Preconditioning by Microwave Hyperthermia on Human Skeletal Muscle After Eccentric Exercise

    PubMed Central

    Saga, Norio; Katamoto, Shizuo; Naito, Hisashi

    2008-01-01

    The purpose of this study was to clarify whether heat preconditioning results in less eccentric exercise-induced muscle damage and muscle soreness, and whether the repeated bout effect is enhanced by heat preconditioning prior to eccentric exercise. Nine untrained male volunteers aged 23 ± 3 years participated in this study. Heat preconditioning included treatment with a microwave hyperthermia unit (150 W, 20 min) that was randomly applied to one of the subject’s arms (MW); the other arm was used as a control (CON). One day after heat preconditioning, the subjects performed 24 maximal isokinetic eccentric contractions of the elbow flexors at 30°·s-1 (ECC1). One week after ECC1, the subjects repeated the procedure (ECC2). After each bout of exercise, maximal voluntary contraction (MVC), range of motion (ROM) of the elbow joint, upper arm circumference, blood creatine kinase (CK) activity and muscle soreness were measured. The subjects experienced both conditions at an interval of 3 weeks. MVC and ROM in the MW were significantly higher than those in the CON (p < 0.05) for ECC1; however, the heat preconditioning had no significant effect on upper arm circumference, blood CK activity, or muscle soreness following ECC1 and ECC2. Heat preconditioning may protect human skeletal muscle from eccentric exercise-induced muscle damage after a single bout of eccentric exercise but does not appear to promote the repeated bout effect after a second bout of eccentric exercise. Key pointsThere have been few studies about the effects of heat preconditioning on muscle damage caused by eccentric exercise and the repeated bout effect after a second bout of eccentric exercise.Heat preconditioning with microwave hyperthermia may attenuate eccentric exercise-induced muscle damage.Heat preconditioning does not enhance the repeated bout effect. PMID:24150151

  7. Coupled electromagnetic-thermodynamic simulations of microwave heating problems using the FDTD algorithm.

    PubMed

    Kopyt, Paweł; Celuch, Małgorzata

    2007-01-01

    A practical implementation of a hybrid simulation system capable of modeling coupled electromagnetic-thermodynamic problems typical in microwave heating is described. The paper presents two approaches to modeling such problems. Both are based on an FDTD-based commercial electromagnetic solver coupled to an external thermodynamic analysis tool required for calculations of heat diffusion. The first approach utilizes a simple FDTD-based thermal solver while in the second it is replaced by a universal commercial CFD solver. The accuracy of the two modeling systems is verified against the original experimental data as well as the measurement results available in literature.

  8. Kinetic resolution of rac-1-phenylethanol with immobilized lipases: a critical comparison of microwave and conventional heating protocols.

    PubMed

    de Souza, Rodrigo Octavio M A; Antunes, Octavio A C; Kroutil, Wolfgang; Kappe, C Oliver

    2009-08-21

    The lipase-catalyzed kinetic resolution of rac-1-phenylethanol with vinyl acetate as acyl donor and cyclohexane as solvent has been investigated applying both microwave dielectric heating and conventional thermal heating in order to probe the existence of nonthermal microwave effects. All transformations were conducted at 40 degrees C in a dedicated reactor setup that allowed accurate internal reaction temperature measurements with use of fiber-optic probes. Quartz reaction vessels that allow higher levels of microwave power to be administered to the reaction mixture were used for all experiments. For all five studied immobilized lipases, the observed reactivities and enantioselectivities in microwave and oil bath experiments were identical and thus not related to the presence of the microwave field. The effect of magnetic stirring proved critical as too rapid stirring in some instances destroyed the enzyme support structure and led to altered reactivities and selectivities.

  9. Ice melting properties of steel slag asphalt concrete with microwave heating

    NASA Astrophysics Data System (ADS)

    Li, Bin; Sun, Yihan; Liu, Quantao; Fang, Hao; Wu, Shaopeng; Tang, Jin; Ye, Qunshan

    2017-03-01

    The ice on the surface of asphalt pavement in winter significantly influences the road transportation safety. This paper aims at the improvement of the ice melting efficiency on the surface of asphalt pavement. The steel slag asphalt concrete was prepared and the high ice melting efficiency was achieved with the microwave heating. A series of experiments were conducted to evaluate the ice melting performance of steel slag asphalt concrete, including the heating test, ice melting test, thermal conductivity test and so on. The results indicated that the microwave heating of steel slag concrete can improve the efficiency of deicing, mainly because the heating rates of steel slag asphalt mixture are much better than traditional limestone asphalt mixture. According to different thickness lever of ice, the final temperatures of each sample were very close to each other at the end of melting test. It is believed the thickness of the ice has a limited impact on the ice melting efficiency. According to the heating tests results, the bonding of ice and asphalt concrete is defined failure at the moment when the surface temperature of the ice reached 3 °C.

  10. Contribution of direct heating, thermal conduction and perfusion during radiofrequency and microwave ablation.

    PubMed

    Schramm, W; Yang, D; Haemmerich, D

    2006-01-01

    Heat based tumor ablation methods such as radiofrequency (RF) and microwave (MW) ablation are increasingly accepted treatment methods for tumors not treatable by traditional surgery. Typically, an interstitial applicator is introduced under imaging guidance into the tumor, and tissue is destroyed by heating to above approximately 50 degrees C, with maximum tissue temperatures over 100 degrees C. Since high thermal gradients occur during the procedure, thermal conduction contributes significantly towards tissue heating. We created finite element method (FEM) computer models of RF and MW applicators, and determined the thermal conduction term, the resistive (for RF) or dielectric (for MW) loss term, and perfusion term. We integrated these terms over the heating period to obtain relative contribution towards tissue temperature rise (in degrees C) as a function of distance from the applicator. We performed simulations without and with perfusion, where perfusion was assumed to stop above 50 degrees C. During the first 6 minutes, direct heating by RF and MW were dominating throughout the tissue. Over the treatment period (12 min for RF, and 6 min for MW), thermal conduction was dominating at distances between than 12 and 19 mm from the RF electrode, while for MW ablation direct heating dominated everywhere. Even though thermal conduction significantly contributes towards tissue heating during ablative therapies, direct heating by RF or MW is dominating throughout most of the tissue volume. Tissue cooling due to perfusion is more significant during RF heating, in part due to the longer treatment times.

  11. Superficial heat reduction technique for a hybrid microwave-optical device.

    PubMed

    Al-Armaghany, A; Tong, K; Leung, T S

    2013-01-01

    Microwave applicator in the form of a circularly polarized microstrip patch antenna is proposed to provide localized deep heating in biological tissue, which causes blood vessels to dilate leading to changes in tissue oxygenation. These changes are monitored by an integrated optical system for studying thermoregulation in different parts of the human body. Using computer simulations, this paper compares circularly and linearly polarized antennas in terms of the efficiency of depositing electromagnetic (EM) energy and the heating patterns. The biological model composes of the skin, fat and muscle layers with appropriate dielectric and thermal properties. The results show that for the same specific absorption rate (SAR) in the muscle, the circularly polarized antenna results in a lower SAR in the skin-fat interface than the linearly polarized antenna. The thermal distribution is also presented based on the biological heat equation. The proposed circularly polarized antenna shows heat reduction in the superficial layers in comparison to the linearly polarized antenna.

  12. EBSD characterization of the growth mechanism of SiC synthesized via direct microwave heating

    SciTech Connect

    Wang, Jigang; Huang, Shan; Liu, Song; Qing, Zhou

    2016-04-15

    Well-crystallized 3C-silicon carbide (SiC) grains/nanowires have been synthesized rapidly and conveniently via direct microwave heating, simply using silicon dioxide powders and artificial graphite as raw materials. The comprehensive characterizations have been employed to investigate the micro-structure of the obtained 3C-SiC products. Results indicated that, different from the classic screw dislocation growth mechanism, the 3C-SiC grains/nanowires synthesized via high-energy vacuum microwave irradiation were achieved through the two-dimension nucleation and laminar growth mechanism. Especially, the electron backscattered diffraction (EBSD) was employed to characterize the crystal planes of the as-grown SiC products. The calculated Euler angles suggested that the fastest-growing crystal planes (211) were overlapped gradually. Through the formation of the (421) transformation plane, (211) finally evolved to (220) which existed as the side face of SiC grains. The most stable crystal planes (111) became the regular hexagonal planes in the end, which could be explained by the Bravais rule. The characterization results of EBSD provided important experimental information for the evolution of crystal planes. - Graphical abstract: The formation of 3C-SiC prepared via direct microwave heating follows the mechanism of two-dimension nucleation and laminar growth. - Highlights: • 3C−SiC grains/nanowires were obtained via direct microwave heating. • 3C−SiC followed the mechanism of two-dimension nucleation and laminar growth. • In-situ EBSD analysis provided the experimental evidences of the growth.

  13. Mantle Convection in a Microwave Oven: New Perspectives for the Internally Heated Convection

    NASA Astrophysics Data System (ADS)

    Limare, A.; Fourel, L.; Surducan, E.; Neamtu, C.; Surducan, V.; Vilella, K.; Farnetani, C. G.; Kaminski, E. C.; Jaupart, C. P.

    2015-12-01

    The thermal evolution of silicate planets is primarily controlled by the balance between internal heating - due to radioactive decay - and heat transport by mantle convection. In the Earth, the problem is particularly complex due to the heterogeneous distribution of heat sources in the mantle and the non-linear coupling between this distribution and convective mixing. To investigate the behaviour of such systems, we have developed a new technology based on microwave absorption to study internally-heated convection in the laboratory. This prototype offers the ability to reach the high Rayleigh-Roberts and Prandtl numbers that are relevant for planetary convection. Our experimental results obtained for a uniform distribution of heat sources were compared to numerical calculations reproducing exactly experimental conditions (3D Cartesian geometry and temperature-dependent physical properties), thereby providing the first cross validation of experimental and numerical studies of convection in internally-heated systems. We find that the thermal boundary layer thickness and interior temperature scale with RaH-1/4, where RaH is the Rayleigh-Roberts number, as theoretically predicted by scaling arguments on the dissipation of kinetic energy. Our microwave-based method offers new perspectives for the study of internally-heated convection in heterogeneous systems which have been out of experimental reach until now. We are able to selectively heat specific regions in the convecting layer, through the careful control of the absorption properties of different miscible fluids. This is analogous to convection in the presence of chemical reservoirs with different concentration of long-lived radioactive isotopes. We shall show results for two different cases: the stability of continental lithosphere over a convective fluid and the evolution of a hidden enriched reservoir in the lowermost mantle.

  14. Development of a compact cylindrical reaction cavity for a microwave dielectric heating system.

    PubMed

    Kim, Myungsik; Kim, Kwangsoo

    2012-03-01

    This paper describes a compact reaction cavity for a microwave-assisted synthesis system. The microwave dielectric heating is a key technology to improve synthesizing yield, however, the large size of the microwave generation and reaction parts in an all-in-one system is a major obstacle when applying the technique to various systems, of which the installation space is limited. For this particular problem, a compact stand-alone cylindrical reaction cavity was developed in the current study. A microwave excited from a monopole probe, which is inserted into the side of the cavity, is transferred to a reaction mixture through the upper hole of the cavity. The cavity is miniaturized by filling it with an alumina ceramic dielectric. Fine-tuning of the resonance frequency becomes available by controlling the length of the inserted screw between the probe and the upper hole. The physical properties of the cavity were simulated using high frequency structural simulator (HFSS) and the produced cavity was tested using an Agilent E8357A network analyzer. The test results show that the developed cavity is able to send enough energy to various solvents.

  15. Temperature measurements with two different IR sensors in a continuous-flow microwave heated system

    PubMed Central

    Rydfjord, Jonas; Svensson, Fredrik; Fagrell, Magnus; Sävmarker, Jonas; Thulin, Måns

    2013-01-01

    Summary In a continuous-flow system equipped with a nonresonant microwave applicator we have investigated how to best assess the actual temperature of microwave heated organic solvents with different characteristics. This is non-trivial as the electromagnetic field will influence most traditional methods of temperature measurement. Thus, we used a microwave transparent fiber optic probe, capable of measuring the temperature inside the reactor, and investigated two different IR sensors as non-contact alternatives to the internal probe. IR sensor 1 measures the temperature on the outside of the reactor whilst IR sensor 2 is designed to measure the temperature of the fluid through the borosilicate glass that constitutes the reactor wall. We have also, in addition to the characterization of the before mentioned IR sensors, developed statistical models to correlate the IR sensor reading to a correct value of the inner temperature (as determined by the internal fiber optic probe), thereby providing a non-contact, indirect, temperature assessment of the heated solvent. The accuracy achieved with these models lie well within the range desired for most synthetic chemistry applications. PMID:24204419

  16. [Comparison of the acrylamide level in microwaved popcorn with that of ordinarily heated one].

    PubMed

    Sun, Shiyu; Xia, Yongmei; Liu, Xuefeng; Hu, Xueyi

    2007-03-01

    To establish a method of examining acrylamide in cooked popcorn. Solid phase extraction/gas chromatography (SPE/GC) was established with N, N-dimethyl acrylamide as internal standard. The detection limit and the quantification limit were estimated at 3 microg/L and 10 microg/L, respectively, and the linear correlation coefficient was 0.9969. Seven commercial popcorn samples with different flavors were collected and tested in this paper. The RSD of acrylamide level of caramel sweet popcorn microwaved was 1.95 % (n = 6). When the commercial popcorns of caramel sweet and cream salted were microwaved (A and D) or conventional heated (A' and D'), the acrylamide levels reached [Am]A = 1017 microg/kg, [Am]D = 146.5 microg/kg, [Am]A, = 2206 microg/kg and [Am]D = 970.1 microg/kg, respectively. The microwaved popcorns tested are safer in general because the acrylamide level of them except that with high simple sugar content is obviously lower than that of ordinarily heated one.

  17. Temperature measurements with two different IR sensors in a continuous-flow microwave heated system.

    PubMed

    Rydfjord, Jonas; Svensson, Fredrik; Fagrell, Magnus; Sävmarker, Jonas; Thulin, Måns; Larhed, Mats

    2013-01-01

    In a continuous-flow system equipped with a nonresonant microwave applicator we have investigated how to best assess the actual temperature of microwave heated organic solvents with different characteristics. This is non-trivial as the electromagnetic field will influence most traditional methods of temperature measurement. Thus, we used a microwave transparent fiber optic probe, capable of measuring the temperature inside the reactor, and investigated two different IR sensors as non-contact alternatives to the internal probe. IR sensor 1 measures the temperature on the outside of the reactor whilst IR sensor 2 is designed to measure the temperature of the fluid through the borosilicate glass that constitutes the reactor wall. We have also, in addition to the characterization of the before mentioned IR sensors, developed statistical models to correlate the IR sensor reading to a correct value of the inner temperature (as determined by the internal fiber optic probe), thereby providing a non-contact, indirect, temperature assessment of the heated solvent. The accuracy achieved with these models lie well within the range desired for most synthetic chemistry applications.

  18. Complete FDTD analysis of microwave heating processes in frequency-dependent and temperature dependent media

    SciTech Connect

    Torres, F.; Jecko, B.

    1997-01-01

    It is well known that the temperature rise in a material modifies its physical properties and, particularly, its dielectric permittivity. The dissipated electromagnetic power involved in microwave heating processes depending on {var_epsilon}({omega}), the electrical characteristics of the heated media must vary with the temperature to achieve realistic simulations. In this paper, the authors present a fast and accurate algorithm allowing, through a combined electromagnetic and thermal procedure, to take into account the influence of the temperature on the electrical properties of materials. First, the temperature dependence of the complex permittivity ruled by a Debye relaxation equation is investigated, and a realistic model is proposed and validated. Then, a frequency-dependent finite-differences time-domain ((FD){sup 2}TD) method is used to assess the instantaneous electromagnetic power lost by dielectric hysteresis. Within the same iteration, a time-scaled form of the heat transfer equation allows one to calculate the temperature distribution in the heated medium and then to correct the dielectric properties of the material using the proposed model. These new characteristics will be taken into account by the EM solver at the next iteration. This combined algorithm allows a significant reduction of computation time. An application to a microwave oven is proposed.

  19. Potential risk of bisphenol A migration from polycarbonate containers after heating, boiling, and microwaving.

    PubMed

    Lim, Duck Soo; Kwack, Seung Jun; Kim, Kyu-Bong; Kim, Hyung Sik; Lee, Byung Mu

    2009-01-01

    The migration levels of bisphenol A (BPA) were analyzed in food samples by high-performance liquid chromatography (HPLC) from polycarbonate (PC) bottles subjected to simulated use by heating with microwave, heating in a boiling water bath, or filling them with boiling hot water (100 degrees C). Migration testing performed in PC bottles filled with steamed rice or hot cooked pork, standing at room temperature, or heated in a boiling water bath (100 degrees C) showed that BPA was not detected at the limit of detection (LOD) of 1 microg/L (ppb). In contrast, heating by microwaving to 100 degrees C for 9 min increased BPA migration levels from 6 to 18 ppb and from 5 to 15 ppb for steamed rice or for cooked pork, respectively. In addition, 3 different PC bottles were tested by filling them with boiling hot water (100 degrees C) and leaving them to stand at room temperature for up to 3 h. The mean BPA levels from the bottles increased in a time-dependent manner, with the range of not detected (ND) to 2.5 ppb after 60 min. However, none of the PC bottles released BPA at levels that exceed the recently established specific migration limits (SML) of 600 ppb established by European Union and Korea Food and Drug Administration (KFDA). Data suggest that the use of PC plastic bottles in our daily life is considered safe in Korea.

  20. Improving heating uniformity of pathological tissue specimens inside a domestic microwave oven.

    PubMed

    Hassan, Osama A; Kandil, Ahmed H; El Bialy, Ahmed M; Hassaballa, Iman A

    2013-01-01

    A 3D coupled electromagnetic thermal model was developed using COMSOL 4.0 to predict the electromagnetic field distribution and temperature profile in pathological tissue samples immersed in a reagent inside the oven cavity. The effect of the volume of reagent on the mean heating rate and heating uniformity within the tissue sample was investigated. Also, the effect of using a water load, as a method of temperature control, is emphasized. A well insulated K type thermocouple connected to a PC is used for model validation. Good agreement is found between experimental and simulated temperature profiles. Results show that as the volume of reagent increases, the mean heating rate decreases and temperature homogeneity increases. Also, it is possible to minimize overshooting temperature values inside the tissue sample and enhance tissue uniformity by about 27% using 100 ml of water load and 42.26% using 150 ml. Domestic microwave oven is a low cost economical tool that can speed up tissue processing steps. Achieving uniform heating inside the microwave oven is the key factor for improving workflow inside pathological labs and maintaining tissue quality and integrity.

  1. Multiphysics Modeling of Microwave Heating of a Frozen Heterogeneous Meal Rotating on a Turntable.

    PubMed

    Pitchai, Krishnamoorthy; Chen, Jiajia; Birla, Sohan; Jones, David; Gonzalez, Ric; Subbiah, Jeyamkondan

    2015-12-01

    A 3-dimensional (3-D) multiphysics model was developed to understand the microwave heating process of a real heterogeneous food, multilayered frozen lasagna. Near-perfect 3-D geometries of food package and microwave oven were used. A multiphase porous media model combining the electromagnetic heat source with heat and mass transfer, and incorporating phase change of melting and evaporation was included in finite element model. Discrete rotation of food on the turntable was incorporated. The model simulated for 6 min of microwave cooking of a 450 g frozen lasagna kept at the center of the rotating turntable in a 1200 W domestic oven. Temperature-dependent dielectric and thermal properties of lasagna ingredients were measured and provided as inputs to the model. Simulated temperature profiles were compared with experimental temperature profiles obtained using a thermal imaging camera and fiber-optic sensors. The total moisture loss in lasagna was predicted and compared with the experimental moisture loss during cooking. The simulated spatial temperature patterns predicted at the top layer was in good agreement with the corresponding patterns observed in thermal images. Predicted point temperature profiles at 6 different locations within the meal were compared with experimental temperature profiles and root mean square error (RMSE) values ranged from 6.6 to 20.0 °C. The predicted total moisture loss matched well with an RMSE value of 0.54 g. Different layers of food components showed considerably different heating performance. Food product developers can use this model for designing food products by understanding the effect of thickness and order of each layer, and material properties of each layer, and packaging shape on cooking performance. © 2015 Institute of Food Technologists®

  2. Modulation of heat shock protein response in SH-SY5Y by mobile phone microwaves

    PubMed Central

    Calabrò, Emanuele; Condello, Salvatore; Currò, Monica; Ferlazzo, Nadia; Caccamo, Daniela; Magazù, Salvatore; Ientile, Riccardo

    2012-01-01

    AIM: To investigate putative biological damage caused by GSM mobile phone frequencies by assessing electromagnetic fields during mobile phone working. METHODS: Neuron-like cells, obtained by retinoic-acid-induced differentiation of human neuroblastoma SH-SY5Y cells, were exposed for 2 h and 4 h to microwaves at 1800 MHz frequency bands. RESULTS: Cell stress response was evaluated by MTT assay as well as changes in the heat shock protein expression (Hsp20, Hsp27 and Hsp70) and caspase-3 activity levels, as biomarkers of apoptotic pathway. Under our experimental conditions, neither cell viability nor Hsp27 expression nor caspase-3 activity was significantly changed. Interestingly, a significant decrease in Hsp20 expression was observed at both times of exposure, whereas Hsp70 levels were significantly increased only after 4 h exposure. CONCLUSION: The modulation of the expression of Hsps in neuronal cells can be an early response to radiofrequency microwaves. PMID:22371824

  3. Stability and Demulsification of Water-in-Crude Oil (w/o) Emulsions Via Microwave Heating

    NASA Astrophysics Data System (ADS)

    Nour, Abdurahman. H.; Rosli; Yunus, Mohd.

    Formation of emulsions during oil production and processing is a costly problem, both in terms of chemicals used and production losses. Experimental data are presented to show the influences of Triton X-100, Low sulphur Wax Residue (LSWR), Sorbitan monooleate (Span 83) and Sodium Dedocyl Sulphate (SDDS) on the stability and microwave demulsification of emulsions. It was found that emulsion stability was related to some parameters such as, the surfactant concentrations, water-oil phase ratio (10-90%), temperature and agitation speed. For economic and operational reasons, it is necessary to separate the water completely from the crude oils before transporting or refining them. In this regard, the present study found that microwave radiation method can enhance the demulsification of water-in-oil (w/o) emulsions in a very short time compared to the conventional heating methods.

  4. Preliminary Study of Heat Supply during Carbon Nanodots Synthesis by Microwave-assisted Method

    NASA Astrophysics Data System (ADS)

    Nakul, F.; Aimon, A. H.; Nuryadin, B. W.; Iskandar, F.

    2016-08-01

    Carbon nanodots (CNDs) are known to be good phosphor materials with wide range emission band, low cytotoxicity and excellent biocompatibility. In this work, CNDs were synthesized from a precursor consisting of citric acid [C6H8O7] as carbon source and urea [(NH2)2CO] as nitrogen source through a microwave-assisted method. The heat energy supplied during the microwave process was controlled. Further, we studied the effect of citric acid mass on the photoluminescence (PL) properties of the CNDs by varying its percentage in the precursors. The optimum luminescence intensity was obtained from the sample that was produced from 1.2 wt% citric acid mass. It had a single emission band with bright yellow luminescence.

  5. A study of some inherent causes for non-uniform microwave heating

    NASA Astrophysics Data System (ADS)

    Tsai, Y. F.; Barnett, L. R.; Teng, H. H.; Ko, C. C.; Chu, K. R.

    2017-10-01

    Radio frequency and microwave heating of dielectric objects is often susceptible to an excessive temperature spread due to uneven energy deposition. The exposure to a non-uniform field is a well-studied cause for this difficulty encountered in numerous applications. There are, however, some less-understood causes, which are inherent in nature in that they persist even in a perfectly uniform field. We present an experimental study on three main inherent causes with rice grains as samples. Experiments are conducted in an applicator, in which samples are irradiated by a 24 GHz microwave. High radiation uniformity (˜99%) and polarization control allow a quantitative examination of each cause. Their individual and collective effects are found to be highly significant. In particular, polarization-charge shielding alone can result in a temperature spread of ˜18.2% for the samples examined. Physical interpretations are given and an effective method for its mitigation is demonstrated.

  6. Rapid ZnO nanopillar array growth by microwave assisted heating

    NASA Astrophysics Data System (ADS)

    Yao, Jimmy; Chang, Yun-Ching; Mei, Hao; Cheng, Jiping; Yin, Stuart (Shizhuo); Luo, Claire

    2010-08-01

    Zinc oxide (ZnO) nano-wires have draw people's attention in recent studies. The unique structural and physical properties offer fascinating potential for future technological applications. The state-of-the-art fabrication process of ZnO nano-wires is based on vapor-liquid-solid (VLS) method. In this paper, the microwave assisted heating technique is introduced for the growth of ZnO nanopillar arrays. The microwave grown ZnO nanowires were characterized by fieldemission scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and photoluminescence spectroscopy. It was demonstrated that (001) oriented single crystal ZnO nanowires can be grown vertically and uniformly on a-plane sapphire wafers.

  7. Numerical simulations of microwave heating of liquids: enhancements using Krylov subspace methods

    NASA Astrophysics Data System (ADS)

    Lollchund, M. R.; Dookhitram, K.; Sunhaloo, M. S.; Boojhawon, R.

    2013-04-01

    In this paper, we compare the performances of three iterative solvers for large sparse linear systems arising in the numerical computations of incompressible Navier-Stokes (NS) equations. These equations are employed mainly in the simulation of microwave heating of liquids. The emphasis of this work is on the application of Krylov projection techniques such as Generalized Minimal Residual (GMRES) to solve the Pressure Poisson Equations that result from discretisation of the NS equations. The performance of the GMRES method is compared with the traditional Gauss-Seidel (GS) and point successive over relaxation (PSOR) techniques through their application to simulate the dynamics of water housed inside a vertical cylindrical vessel which is subjected to microwave radiation. It is found that as the mesh size increases, GMRES gives the fastest convergence rate in terms of computational times and number of iterations.

  8. Higher Fe{sup 2+}/total Fe ratio in iron doped phosphate glass melted by microwave heating

    SciTech Connect

    Mandal, Ashis K.; Sinha, Prasanta K.; Das, Dipankar; Guha, Chandan; Sen, Ranjan

    2015-03-15

    Highlights: • Iron doped phosphate glasses prepared using microwave heating and conventional heating under air and reducing atmosphere. • Presence of iron predominantly in the ferrous oxidation state in all the glasses. • Significant concentrations of iron in the ferrous oxidation state on both octahedral and tetrahedral sites in all the glasses. • Ratio of Fe{sup 2+} with total iron is found higher in microwave prepared glasses in comparison to conventional prepared glasses. - Abstract: Iron doped phosphate glasses containing P{sub 2}O{sub 5}–MgO–ZnO–B{sub 2}O{sub 3}–Al{sub 2}O{sub 3} were melted using conventional resistance heating and microwave heating in air and under reducing atmosphere. All the glasses were characterised by UV–Vis–NIR spectroscopy, Mössbauer spectroscopy, thermogravimetric analysis and wet colorimetry analysis. Mössbauer spectroscopy revealed presence of iron predominantly in the ferrous oxidation state on two different sites in all the glasses. The intensity of the ferrous absorption peaks in UV–Vis–NIR spectrum was found to be more in glasses prepared using microwave radiation compared to the glasses prepared in a resistance heating furnace. Thermogravimetric analysis showed increasing weight gain on heating under oxygen atmosphere for glass corroborating higher ratio of FeO/(FeO + Fe{sub 2}O{sub 3}) in glass melted by direct microwave heating. Wet chemical analysis also substantiated the finding of higher ratio Fe{sup +2}/ΣFe in microwave melted glasses. It was found that iron redox ratio was highest in the glasses prepared in a microwave furnace under reducing atmosphere.

  9. Precipitation and Latent Heating Distributions from Satellite Passive Microwave Radiometry. Part 1; Method and Uncertainties

    NASA Technical Reports Server (NTRS)

    Olson, William S.; Kummerow, Christian D.; Yang, Song; Petty, Grant W.; Tao, Wei-Kuo; Bell, Thomas L.; Braun, Scott A.; Wang, Yansen; Lang, Stephen E.; Johnson, Daniel E.

    2004-01-01

    A revised Bayesian algorithm for estimating surface rain rate, convective rain proportion, and latent heating/drying profiles from satellite-borne passive microwave radiometer observations over ocean backgrounds is described. The algorithm searches a large database of cloud-radiative model simulations to find cloud profiles that are radiatively consistent with a given set of microwave radiance measurements. The properties of these radiatively consistent profiles are then composited to obtain best estimates of the observed properties. The revised algorithm is supported by an expanded and more physically consistent database of cloud-radiative model simulations. The algorithm also features a better quantification of the convective and non-convective contributions to total rainfall, a new geographic database, and an improved representation of background radiances in rain-free regions. Bias and random error estimates are derived from applications of the algorithm to synthetic radiance data, based upon a subset of cloud resolving model simulations, and from the Bayesian formulation itself. Synthetic rain rate and latent heating estimates exhibit a trend of high (low) bias for low (high) retrieved values. The Bayesian estimates of random error are propagated to represent errors at coarser time and space resolutions, based upon applications of the algorithm to TRMM Microwave Imager (TMI) data. Errors in instantaneous rain rate estimates at 0.5 deg resolution range from approximately 50% at 1 mm/h to 20% at 14 mm/h. These errors represent about 70-90% of the mean random deviation between collocated passive microwave and spaceborne radar rain rate estimates. The cumulative algorithm error in TMI estimates at monthly, 2.5 deg resolution is relatively small (less than 6% at 5 mm/day) compared to the random error due to infrequent satellite temporal sampling (8-35% at the same rain rate).

  10. Hydrothermal carbonization of sugarcane bagasse via wet torrefaction in association with microwave heating.

    PubMed

    Chen, Wei-Hsin; Ye, Song-Ching; Sheen, Herng-Kuang

    2012-08-01

    Hydrothermal carbonization of sugarcane bagasse using wet torrefaction is studied. The biomass is torrefied in water or dilute sulfuric acid solution and microwaves are employed to heat the solutions where the reaction temperature is fixed at 180 °C. The effects of acid concentration, heating time and solid-to-liquid ratio on the performance of wet torrefaction are investigated. It is found that the addition of sulfuric acid and increasing heating time are conducive to carbonizing bagasse. The calorific value of bagasse can be increased up to 20.3% from wet torrefaction. With the same improvement in calorific value, the temperature of wet torrefaction is lower than that of dry torrefaction around 100 °C, revealing that wet torrefaction is a promising method to upgrade biomass as fuel. The calorific value of torrefied biomass can be predicted well based on proximate, elemental or fiber analysis, and the last one gives the best estimation.

  11. Numerical modeling of continuous flow microwave heating: a critical comparison of COMSOL and ANSYS.

    PubMed

    Salvi, D; Boldor, Dorin; Ortego, J; Aita, G M; Sabliov, C M

    2010-01-01

    Numerical models were developed to simulate temperature profiles in Newtonian fluids during continuous flow microwave heating by one way coupling electromagnetism, fluid flow, and heat transport in ANSYS 8.0 and COMSOL Multiphysics v3.4. Comparison of the results from the COMSOL model with the results from a pre-developed and validated ANSYS model ensured accuracy of the COMSOL model. Prediction of power Loss by both models was in close agreement (5-13% variation) and the predicted temperature profiles were similar. COMSOL provided a flexible model setup whereas ANSYS required coupling incompatible elements to transfer load between electromagnetic, fluid flow, and heat transport modules. Overall, both software packages provided the ability to solve multiphysics phenomena accurately.

  12. Effects of electrical shielding and salt concentration on microwave heating in cylindrical containers.

    PubMed

    Anantheswaran, R C; Swanderski, J L

    2002-01-01

    Time-temperature distributions in water and salt solutions were collected in a cylindrical container with and without electrical top shielding during microwave heating. A cold spot was found to exist for both water and salt solutions close to the bottom of the container with and without electrical top shielding. Surface heating was observed in unshielded salt solutions and resulted in a stagnant layer close to the top of the container. Surface heating was eliminated in salt solutions with electrical shielding at the top of the container. Flow profiles within the container were monitored using a potassium permanganate dye tracer and a video camera. The flow profiles for water showed an upward flow in the central region and a descending flow along the side walls. An upward flow along the side walls and a downward flow along the central axis was observed for salt solutions.

  13. Coupled electromagnetic and thermal modeling of microwave oven heating of foods.

    PubMed

    Zhang, H; Datta, A K

    2000-01-01

    Temperature distributions from heating in a domestic microwave oven were studied by considering the coupling between the electromagnetics and heat transfer through changes in dielectric properties during heating. Maxwell's equations for electromagnetics and the thermal energy equations are solved numerically using two separate finite-element softwares. The coupling between the softwares was developed by writing special modules that interfaced these softwares at the system level. Experimentally measured temperature profiles were compared with the numerical predictions. The importance of coupling was evident when the properties changed significantly with temperature for low and high dielectric loss materials and more so for the high loss materials. For moderate loss materials, when the properties do not change as much with temperature, coupled solutions lead to results very close to the results for the uncoupled solution.

  14. Using microwave heating to improve the desorption efficiency of high molecular weight VOC from beaded activated carbon.

    PubMed

    Fayaz, Mohammadreza; Shariaty, Pooya; Atkinson, John D; Hashisho, Zaher; Phillips, John H; Anderson, James E; Nichols, Mark

    2015-04-07

    Incomplete regeneration of activated carbon loaded with organic compounds results in heel build-up that reduces the useful life of the adsorbent. In this study, microwave heating was tested as a regeneration method for beaded activated carbon (BAC) loaded with n-dodecane, a high molecular weight volatile organic compound. Energy consumption and desorption efficiency for microwave-heating regeneration were compared with conductive-heating regeneration. The minimum energy needed to completely regenerate the adsorbent (100% desorption efficiency) using microwave regeneration was 6% of that needed with conductive heating regeneration, owing to more rapid heating rates and lower heat loss. Analyses of adsorbent pore size distribution and surface chemistry confirmed that neither heating method altered the physical/chemical properties of the BAC. Additionally, gas chromatography (with flame ionization detector) confirmed that neither regeneration method detectably altered the adsorbate composition during desorption. By demonstrating improvements in energy consumption and desorption efficiency and showing stable adsorbate and adsorbent properties, this paper suggests that microwave heating is an attractive method for activated carbon regeneration particularly when high-affinity VOC adsorbates are present.

  15. Gas dynamic model of electrothermal thrusters of small spacecraft and possibility of applying microwave heating of a working

    NASA Astrophysics Data System (ADS)

    Blinov, V. N.; Shalay, V. V.; Vavilov, I. S.; Kositsin, V. V.; Ruban, V. I.; Lykyanchik, A. I.; Yachmenev, P. S.; Vlasov, A. S.

    2017-06-01

    This paper is devoted to development and approbation of the gas dynamic model of ammonia thruster with low power consumption and ultra small thrust for picosatellite weighing up to 5 kg and possibility of applying microwave heating of a working fluid. It is shown, that simplest electrothermal thruster consisting of propellant tank, solenoid valve, expension cavity and heating chamber can provide ultra small trust due to gas dynamic processes and small heat supply. The results of the study set tasks for further design of small spacecrafts microwave generators.

  16. Enhancing oxidative stability of sunflower oil during convective and microwave heating using grape seed extract.

    PubMed

    Poiana, Mariana-Atena

    2012-01-01

    This study was performed to investigate the effectiveness of grape seed extract (GSE) compared to butylated hydroxytoluene (BHT) on retarding lipid oxidation of sunflower oil subjected to convection and microwave heating up to 240 min under simulated frying conditions. The progress of lipid oxidation was assessed in terms of peroxide value (PV), p-anisidine value (p-AV), conjugated dienes and trienes (CD, CT), inhibition of oil oxidation (IO) and TOTOX value. In addition, total phenolic content (TP) was evaluated in samples before and after heating in order to assess the changes in these compounds relative to the extent of lipid oxidation. The results of this study highlight that GSE showed a significantly inhibitory effect on lipid oxidation during both treatments, although to a different extent. This ability was dose-dependent; therefore, the extent of lipid oxidation was inversely related to GSE level. Convective heating, respective microwave exposure for 240 min of samples supplemented by GSE to a level of 1000 ppm, resulted in significant decreases of investigated indices relative to the control values as follows: PV (48%; 30%), p-AV (29%; 40%), CD (45%; 30%), CT (41%; 36%), TOTOX (35%; 37%). GSE to a level of 600-800 ppm inhibited the lipid oxidation in a similar manner to BHT. These results suggested that GSE can be used as a potential natural extract for improving oxidative stability of sunflower oil during thermal applications.

  17. Enhancing Oxidative Stability of Sunflower Oil during Convective and Microwave Heating Using Grape Seed Extract

    PubMed Central

    Poiana, Mariana-Atena

    2012-01-01

    This study was performed to investigate the effectiveness of grape seed extract (GSE) compared to butylated hydroxytoluene (BHT) on retarding lipid oxidation of sunflower oil subjected to convection and microwave heating up to 240 min under simulated frying conditions. The progress of lipid oxidation was assessed in terms of peroxide value (PV), p-anisidine value (p-AV), conjugated dienes and trienes (CD, CT), inhibition of oil oxidation (IO) and TOTOX value. In addition, total phenolic content (TP) was evaluated in samples before and after heating in order to assess the changes in these compounds relative to the extent of lipid oxidation. The results of this study highlight that GSE showed a significantly inhibitory effect on lipid oxidation during both treatments, although to a different extent. This ability was dose-dependent; therefore, the extent of lipid oxidation was inversely related to GSE level. Convective heating, respective microwave exposure for 240 min of samples supplemented by GSE to a level of 1000 ppm, resulted in significant decreases of investigated indices relative to the control values as follows: PV (48%; 30%), p-AV (29%; 40%), CD (45%; 30%), CT (41%; 36%), TOTOX (35%; 37%). GSE to a level of 600–800 ppm inhibited the lipid oxidation in a similar manner to BHT. These results suggested that GSE can be used as a potential natural extract for improving oxidative stability of sunflower oil during thermal applications. PMID:22942764

  18. High-power microwave transmission and launching systems for fusion plasma heating systems

    SciTech Connect

    Bigelow, T.S.

    1989-01-01

    Microwave power in the 30- to 300-GHz frequency range is becoming widely used for heating of plasma in present-day fusion energy magnetic confinement experiments. Microwave power is effective in ionizing plasma and heating electrons through the electron cyclotron heating (ECH) process. Since the power is absorbed in regions of the magnetic field where resonance occurs and launching antennas with narrow beam widths are possible, power deposition location can be highly controlled. This is important for maximizing the power utilization efficiency and improving plasma parameters. Development of the gyrotron oscillator tube has advanced in recent years so that a 1-MW continuous-wave, 140-GHz power source will soon be available. Gyrotron output power is typically in a circular waveguide propagating a circular electric mode (such as TE/sub 0,2/) or a whispering-gallery mode (such as TE/sub 15,2/), depending on frequency and power level. An alternative high-power microwave source currently under development is the free-electron laser (FEL), which may be capable of generating 2-10 MW of average power at frequencies of up to 500 GHz. The FEL has a rectangular output waveguide carrying the TE/sub 0,1/ mode. Because of its higher complexity and cost, the high-average-power FEL is not yet as extensively developed as the gyrotron. In this paper, several types of operating ECH transmission systems are discussed, as well systems currently being developed. The trend in this area is toward higher power and frequency due to the improvements in plasma density and temperature possible. Every system requires a variety of components, such as mode converters, waveguide bends, launchers, and directional couplers. Some of these components are discussed here, along with ongoing work to improve their performance. 8 refs.

  19. Production of bio-fuels by high temperature pyrolysis of sewage sludge using conventional and microwave heating.

    PubMed

    Domínguez, A; Menéndez, J A; Inguanzo, M; Pís, J J

    2006-07-01

    The pyrolysis of sewage sludge was investigated using microwave and electrical ovens as the sources of heat, and graphite and char as microwave absorbers. The main objective of this work was to maximize the gas yield and to assess its quality as a fuel and as a source of hydrogen or syngas (H2 + CO). Both gases were produced in a higher proportion by microwave pyrolysis than by conventional pyrolysis, with a maximum value of 38% for H2 and 66% for H2 + CO. The oils obtained were also characterized using FTIR and GC-MS. The use of conventional electrical heating in the pyrolysis of sewage sludge produced an oil that could have a significant environmental and toxicological impact. Conversely, microwave pyrolysis still preserved some of the functional groups of the initial sludge such as aliphatic and oxygenated compounds, whereas no heavy PACs were detected.

  20. Microwave heating inactivates Shiga Toxin (Stx2) in reconstituted fat-free Milk and adversely affects the nutritional value of cell culture medium

    USDA-ARS?s Scientific Manuscript database

    Microwave exposure is a convenient and widely used method for defrosting, heating, and cooking numerous foods. Microwave cooking is also reported to kill pathogenic microorganisms that often contaminate food. Microwaves act by causing polar molecules in food, such as water, to rapidly rotate, thus...

  1. Dual modification of taro starch by microwave and other heat moisture treatments.

    PubMed

    Deka, Dhritiman; Sit, Nandan

    2016-11-01

    Effect of heat moisture treatment on the physicochemical properties of taro starch with 25% moisture (w/w) modified by single treatments of microwave (HMT1), autoclave (HMT2) and hot air oven (HMT3), and dual treatments of microwave followed by autoclave (HMT4) and microwave followed by hot air oven (HMT5) were investigated. Amylose contents of the modified starches increased except for HMT3. A loss of physical integrity of the starch granules were observed for dual modified starches. The swelling and solubility of all the modified starches increased. The peak viscosities of starches modified by HMT1 and HMT5 were found to be higher whereas for other modified starches it was lower than that of native starch. The holding and final viscosities of all the modified starches except HMT4 were higher than native starch. The freeze-thaw stabilities of the modified starches were also found to be better than that of native starch. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Detection of carbon nanotubes in plant roots through microwave-induced heating

    NASA Astrophysics Data System (ADS)

    Irin, Fahmida; Shrestha, Babina; Canas, Jaclyn; Saed, Mohammad; Green, Micah

    2012-02-01

    We demonstrate a novel technique for quantitative detection of CNTs in biological samples by utilizing the thermal response of CNTs under microwave irradiation. In particular, rapid heating of CNTs due to microwave absorption was employed to quantify the amount of CNTs present in alfalfa plant roots. Alfalfa roots were prepared by injecting a known amount of CNTs (single walled and multi walled) and exposed to 30-50 W microwave power to generate calibration curves (temperature rise vs. CNT mass). These calibration curves serve as a characterization tool to determine the unknown amount of CNTs absorbed by alfalfa plant roots grown in CNT-laden soil with superior accuracy and sensitivity. Moreover, the threshold for detectable CNT concentration is much lower than common analytical methods of detecting nanomaterials, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. Considering the lack of effective detection methods for CNT uptake in plants, this method is not only unique but also practical, as it addresses a major problem in the field of nanotoxicology risk assessment.

  3. Theoretical analysis on pulsed microwave heating of pork meat supported on ceramic plate.

    PubMed

    Basak, Tanmay; Rao, Badri S

    2010-11-01

    Theoretical analysis has been carried out to study the role of ceramic plates (alumina and SiC) and pulsed microwave heating of pork meat (Pork Luncheon Roll (PLR) and White Pudding (WP)) samples. Spatial hot spots occur either at the center of the sample or at the outer face or at the face attached with alumina plate and application of pulsing minimizes formation of hot spots within meat samples. Pulsing of microwave is characterized by set point for temperature difference (ΔTS) and on-off constraints for temperature (T'). It is found that alumina plate with higher ΔTS and lower T' may be recommended for thick meat samples (both WP and PLR) whereas for thin meat samples, lower ΔTS with alumina plate/without plate may be preferred. It is also observed that SiC plate may be selectively used with ΔTS=20K for both the pork meats. The distributed microwave incidence is found to be effective due to lesser degree of thermal runaway in absence of pulsing for both meat samples. Copyright © 2010 The American Meat Science Association. Published by Elsevier Ltd. All rights reserved.

  4. Rapid online nonenzymatic protein digestion combining microwave heating acid hydrolysis and electrochemical oxidation.

    PubMed

    Basile, Franco; Hauser, Nicolas

    2011-01-01

    We report an online nonenzymatic method for site-specific digestion of proteins to yield peptides that are well suited for collision-induced dissociation tandem mass spectrometry. The method combines online microwave heating acid hydrolysis at aspartic acid and online electrochemical oxidation at tryptophan and tyrosine. The combined microwave/electrochemical digestion is reproducible and produces peptides with an average sequence length of 10 amino acids. This peptide length is similar to the average peptide length of 9 amino acids obtained by digestion of proteins with the enzyme trypsin. As a result, the peptides produced by this novel nonenzymatic digestion method, when analyzed by electrospray ionization mass spectrometry, produce protonated molecules with mostly +1 and +2 charge states. The combination of these two nonenzymatic methods overcomes shortcomings with each individual method in that (i) peptides generated by the microwave-hydrolysis method have an average amino acid length of 16 amino acids and (ii) the electrochemical-cleavage method is unable to reproducibly digest proteins with molecular masses above 4 kDa. Preliminary results are presented on the application and utility of this rapid online digestion (total of 6 min of digestion time) on a series of standard peptides and proteins as well as an Escherichia coli protein extract.

  5. Low-temperature synthesis of allyl dimethylamine by selective heating under microwave irradiation used for water treatment

    NASA Astrophysics Data System (ADS)

    Tian, Binghui; Luan, Zhaokun; Li, Mingming

    2005-08-01

    Low-temperature synthesis of allyl dimethylamine (ADA) by selective heating under microwave irradiation (MI) used for water treatment is investigated. The effect of MI, ultrasound irradiation (UI) and conventional heating on yield of ADA, reaction time and the flocculation efficiency of polydiallyl dimethylammunion chloride (PDADMAC) prepared form ADA were studied. The results show that by selective heating at low temperature, MI not only increases yield of ADA and reduces reaction time, but also greatly enhances the flocculation efficiency of PDADMAC.

  6. Microwave-assisted cross-coupling and hydrogenation chemistry by using heterogeneous transition-metal catalysts: an evaluation of the role of selective catalyst heating.

    PubMed

    Irfan, Muhammed; Fuchs, Michael; Glasnov, Toma N; Kappe, C Oliver

    2009-11-02

    The concept of specific microwave effects in solid/liquid catalytic processes resulting from the selective heating of a microwave-absorbing heterogeneous transition-metal catalyst by using 2.45 GHz microwave irradiation was evaluated. As model transformations Ni/C-, Cu/C-, Pd/C-, and Pd/Al2O3-catalyzed carbon-carbon/carbon-heteroatom cross-couplings and hydrogenation reactions were investigated. To probe the existence of specific microwave effects by means of selective catalyst heating in these transformations, control experiments comparing microwave dielectric heating and conventional thermal heating at the same reaction temperature were performed. Although the supported metal catalysts were experimentally found to be strongly microwave absorbing, for all chemistry examples investigated herein no differences in reaction rate or selectivity between microwave and conventional heating experiments under carefully controlled conditions were observed. This was true also for reactions that use low-absorbing or microwave transparent solvents, and was independent of the microwave absorbtivity of the catalyst support material. In the case of hydrogenation reactions, the stirring speed was found to be a critical factor on the mass transfer between gas and liquid phase, influencing the rate of the hydrogenation in both microwave and conventionally heated experiments.

  7. Rapid alkali catalyzed transesterification of microalgae lipids to biodiesel using simultaneous cooling and microwave heating and its optimization.

    PubMed

    Chee Loong, Teo; Idris, Ani

    2014-12-01

    Biodiesel with improved yield was produced from microalgae biomass under simultaneous cooling and microwave heating (SCMH). Nannochloropsis sp. and Tetraselmis sp. which were known to contain higher lipid species were used. The yield obtained using this novel technique was compared with the conventional heating (CH) and microwave heating (MWH) as the control method. The results revealed that the yields obtained using the novel SCMH were higher; Nannochloropsis sp. (83.33%) and Tetraselmis sp. (77.14%) than the control methods. Maximum yields were obtained using SCMH when the microwave was set at 50°C, 800W, 16h of reaction with simultaneous cooling at 15°C; and water content and lipid to methanol ratio in reaction mixture was kept to 0 and 1:12 respectively. GC analysis depicted that the biodiesel produced from this technique has lower carbon components (<19 C) and has both reasonable CN and IV reflecting good ignition and lubricating properties.

  8. Microwave heating effects on the chemical composition and the antioxidant capacity of tataouine virgin olive oils from Tunisia.

    PubMed

    Oueslati, Imen; Taamalli, Wael; Haddada, Faouzia M; Zarrouk, Mokhtar

    2010-10-01

    Four Tunisian virgin olive oils (VOOs), derived from varieties (Chemlali Tataouine, Zarrazi Douirat, Fakhari Douirat, and Dhokar Douirat) grown in the harsh pedoclimatic conditions of the region of Tataouine, were evaluated for their responses to microwave heating. Aside from fatty acid composition, all other evaluated parameters were affected by microwave heating, and their variations depend on the genetic factor. Chemlali Tataouine VOO exhibited the slowest biophenol degradation rate and the least diminution in oxidative stability and consequently, its total fraction and both lipidic and methanolic fractions remained unchanged with an exceptional antioxidant potential. In the remaining studied VOOs, the biophenol contents, the oxidative stability, and the antioxidant potential underwent gradual decreases; nevertheless, their levels at the longer treatment time are close to some fresh VOOs. These results should be taken into consideration when Tataouine VOOs are recommended for microwave heating.

  9. In situ growth of silver nanoparticles on TEMPO-oxidized jute fibers by microwave heating.

    PubMed

    Cao, Xinwang; Ding, Bin; Yu, Jianyong; Al-Deyab, Salem S

    2013-01-30

    Cellulose fibers deposited with metallic nanoparticles as one kind of renewable, biocompatible and antimicrobial nanomaterials evoke much interest because of their versatility in various applications. Herein, for the first time, a facile, simple and rapid method was developed to fabricate TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) selectively oxidized jute fibers in situ deposited with silver nanoparticles in the absence of reducing reagents. The average size of silver nanoparticles deposited on the fibers is 50.0 ± 2.0 nm by microwave heating for 5 min and 90.0 ± 4.7 nm for 10 min heating sample, respectively. The versatile jute-silver nanoparticles nanocomposites with superior thermal stability and high crystallinity would be particularly useful for applications in the public health care and biomedical fields.

  10. Optimization of hydrous ferrous sulfate dehydration by microwave heating using response surface methodology.

    PubMed

    Yu, Yan-Tao; Liu, Bing-Guo; Chen, Guo; Peng, Jin-Hui; Srinivasakannan, C

    2012-01-01

    The work relates to assessing the ability of the microwave for dehydration of large amount of waste hydrous ferrous sulfate generated from the titanium pigment process industry. The popular process optimization tool of response surface methodology with central composite design was adopted to estimate the effect of dehydration. The process variables were chosen to be power input, duration of heating and the bed thickness, while the response variable being the weight loss. An increase in all the three process variables were found to significantly increase the weight loss, while the effect of interaction among the parameters were found to be insignificant. The optimized process conditions that contribute to the maximum weight loss were identified to be a power input of 960 W, duration of heating of 14 min and bed thickness of 5 cm, resulting in a weight loss of 31.44%. The validity of the optimization process was tested with the repeat runs at optimized conditions.

  11. Enhanced microwave absorbing properties and heat resistance of carbonyl iron by electroless plating Co

    NASA Astrophysics Data System (ADS)

    Wang, Hongyu; Zhu, Dongmei; Zhou, Wancheng; Luo, Fa

    2015-11-01

    Co coated carbonyl iron particles (Co (CI)) are fabricated through electroless plating method, and the electromagnetic microwave absorbing properties are investigated in the frequencies during 8.2-12.4 GHz. The complex permittivity of CI particles after electroless plating Co is higher than that of raw CI particles due to improvment of the polarization process. Furthermore, according to the XRD and TG results, the Co layer can enhance the heat resistance of CI particles. The bandwidth below -10 dB can reach 3.9 GHz for the Co(CI) absorbent. The results indicate that the electroless plating Co not only enhances the absorbing properties but also improves the heat resistance of CI.

  12. Quasi-optical theory of microwave plasma heating in open magnetic trap

    NASA Astrophysics Data System (ADS)

    Shalashov, A. G.; Balakin, A. A.; Gospodchikov, E. D.; Khusainov, T. A.

    2016-11-01

    Microwave heating of a high-temperature plasma confined in a large-scale open magnetic trap, including all important wave effects like diffraction, absorption, dispersion, and wave beam aberrations, is described for the first time within the first-principle technique based on consistent Maxwell's equations. With this purpose, the quasi-optical approach is generalized over weakly inhomogeneous gyrotrotropic media with resonant absorption and spatial dispersion, and a new form of the integral quasi-optical equation is proposed. An effective numerical technique for this equation's solution is developed and realized in a new code QOOT, which is verified with the simulations of realistic electron cyclotron heating scenarios at the Gas Dynamic Trap at the Budker Institute of Nuclear Physics (Novosibirsk, Russia).

  13. Pulsed microwave heating method for preparation of dye-sensitized solar cells for greener, faster, cheaper production of photovoltaic materials

    NASA Astrophysics Data System (ADS)

    Murphy, Clifford B.; Cotta, Robert; Blais, Timothy; Hall, Charles B.

    2015-05-01

    Microwave heating methods are very popular for developing chemical syntheses that are achieved much more rapidly or with less solvent than via conventional heating methods. Their application to solar cell development has been primarily in developing improvements in the synthesis of dyes and curing of polymer substrates, but not in assisting the photoanode construction of dye-sensitized solar cells. Microwave heating of conducting substrates can lead to arcing of electricity in the reactor, which in turn, can lead to extensive degradation or complete destruction of the photoanode. Here we present our work in applying a pulsed microwave heating method that affords quicker dye deposition times in comparison to conventional heating (μw 40 min, conventional 60 min) with similar dye concentrations as characterized by UV-Vis absorbance, contact angle measurements, and cyclic voltammetry. Our photoanodes are constructed with anatase TiO2 cured onto FTO glass, and deposition of the N719 ruthenium dye either directly to the TiO2 layer or through amide bond formation to a silane layer that has been deposited on the TiO2 layer. Modest improvements in the solar energy conversion efficiency are shown through the microwave method in comparison to conventional heating (μw 0.78% vs. conventional 0.25% reported by K. Szpakolski, et. Al. Polyhedron, 2013, 52, 719-732.)

  14. Effect of microwave heating on BaTiO3:Nb ceramics with positive temperature coefficient of resistivity

    NASA Astrophysics Data System (ADS)

    Jida, Shin'suke; Suemasu, Takeshi; Miki, Toshikatsu

    1999-08-01

    The microwave heating technique is employed for obtaining high performance positive temperature coefficient of resistivity (PTCR) ceramics of Nb-doped BaTiO3 with a low resistivity at room temperature and a high resistivity jump above the Curie temperature. The grains of the BaTiO3:Nb ceramics prepared by microwave sintering are as large as 20-50 μm even when the Nb content exceeds 0.2 at. %, whereas such large grain size has never been obtained at this high content of Nb by ordinary sintering with an electric furnace. The large grains are also obtained by subjecting the heavily Nb-doped ceramics composed of fine grains to postheating with microwave after ordinary sintering. The room-temperature resistivity decreases down below 10 Ω cm and the PTCR character is obtained by postannealing in air. The mechanism of grain growth by microwave heating is discussed in terms of nonuniform temperature distribution of specimens during heating. The experimental data indicate that the microwave heating technique and the employment of a dopant that forms donor levels even at high doping levels will enable to develop high performance PTCR ceramics.

  15. Microwave oven heating for inactivation of Listeria monocytogenes on frankfurters before consumption.

    PubMed

    Rodríguez-Marval, Mawill; Geornaras, Ifigenia; Kendall, Patricia A; Scanga, John A; Belk, Keith E; Sofos, John N

    2009-10-01

    Microwave oven heating was evaluated for inactivation of Listeria monocytogenes on inoculated and stored frankfurters. Frankfurters formulated without/with 1.5% potassium lactate and 0.1% sodium diacetate were inoculated with L. monocytogenes (1.9 +/- 0.2 log CFU/cm(2)), vacuum-packaged, and stored (4 degrees C) to simulate conditions prior to purchase by consumers. At storage days 18, 36, and 54, packages were opened and placed at 7 degrees C, simulating aerobic storage in a household refrigerator. At 0, 3, and 7 d of aerobic storage, 2 frankfurters were placed in a bowl with water (250 mL) and treated in a household microwave oven at high (1100 W) power for 30, 45, 60, or 75 s, or medium (550 W) power for 60 or 75 s. Frankfurters and the heating water were analyzed for total microbial counts and L. monocytogenes populations. Exposure to high power for 75 s reduced pathogen levels (0.7 +/- 0.0 to 1.0 +/- 0.1 log CFU/cm(2)) to below the detection limit (<-0.4 log CFU/cm(2)) on frankfurters with lactate/diacetate, even after 54 d of vacuum-packaged storage followed by 7 d of aerobic storage. For frankfurters without lactate/diacetate, high power for 75 s caused reductions between > 1.5 and 5.9 log CFU/cm(2) from control levels of 1.5 +/- 0.1 to 7.2 +/- 0.5 log CFU/cm(2). Depending on treatment and storage time, the water used to reheat the frankfurters had viable L. monocytogenes counts of <-2.4 to 5.5 +/- 0.5 log CFU/mL. The results indicated that frankfurters should be reheated in a microwave oven at high power for 75 s to inactivate up to 3.7 log CFU/cm(2) of L. monocytogenes contamination.

  16. Application of microwave radiation to biofilm heating during wastewater treatment in trickling filters.

    PubMed

    Zieliński, Marcin; Zielińska, Magdalena; Dębowski, Marcin

    2013-01-01

    The purpose of this study was to demonstrate the potential for improving wastewater treatment by the application of microwave radiation (MW) compared to convective heating (CH) of trickling filters. Microwaves were delivered to the biofilm in a continuous and intermittent way to obtain temperatures of 20, 25, 35 and 40 °C. Although there was no effect of MW on organic removal, the observed yield coefficient was lower during the continuous MW supply compared to the periodic dosage and CH. The presence of organic compounds in the influent and continuous biofilm exposure to MW resulted in ca. 10% higher efficiency and ca. 20% higher rate of nitrification compared to intermittent MW dosage and CH. Independent of the method of reactor heating, the absence of organic carbon in the influent induced a significant increase in ammonium oxidation efficiency at 20-35 °C. Despite the aerobic conditions in trickling filters, nitrogen loss was observed. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. Effect of microwave-assisted dry heating with xanthan on normal and waxy corn starches.

    PubMed

    Sun, Qingjie; Xu, Yicai; Xiong, Liu

    2014-07-01

    Normal corn starch (CS) and waxy corn starch (WCS) were impregnated with xanthan gum (1% based on starch) and heat-treated using a microwave in a dry state for 0, 4, or 6min (CS-X0, CS-X4, CS-X6, WCS-X0, WCS-X4, WCS-X6), respectively. Effects of the microwave-assisted dry heating (MADH) on pasting, morphological, and structural properties were evaluated. The results revealed that the viscosity of both the CS and WCS with xanthan increased compared with untreated samples after MADH, and the effect on WCS was more obvious. The syneresis values showed that the water-holding ability of CS-X6 and WCS-X6 increased, and that value of CS was lower than that of WCS after MADH with xanthan. The MADH with xanthan reduced the To, Tc, Tp, and ΔH values of both the CS and WCS. After MADH, the particle morphology of the starch-xanthan connected more densely, especially WCS, and the gelatinized samples exhibited a strong and smooth laminar structure. The Fourier transform Infrared Spectroscopy (FTIR) displayed that the absorption peak width of both CS-X6 and WCS-X6 became larger. X-ray diffraction showed that the crystallinity of CS-X6 and WCS-X6 decreased slightly as a result of MADH, and the crystalline pattern remained A-type. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Comparison of Microwave and Conventional Heating of a Wheat Starch-Gluten Model System

    NASA Astrophysics Data System (ADS)

    Umbach, Sharon Lynn

    The effects of conventional (CV) and microwave (MW) heating on a model wheat starch, vital wheat gluten system were studied. Three moisture contents (35%, 50%, and 65%) and up to five ratios of starch:gluten were studied. MW power was such that heating took place more quickly than during CV heating conditions. Temperature profiles during heating showed the importance of moisture content for curve shape and that all samples reached a high enough temperature for starch gelatinization and gluten denaturation to occur. Scanning electron microscopy supported temperature data in that physical changes for starch had taken place. Texture was evaluated as the force required to compress the sample. Differences were found for heating method, moisture content, and sample composition. Moisture content had the major effect and was inversely related to force. In general, CV heated samples required more force to compress than the MW heated samples. The high starch samples at 50% moisture showed the opposite affect. Self-diffusion coefficients determined by nuclear magnetic resonance (NMR) showed that there was a redistribution of water between starch and gluten after heating for the faster more mobile water in the samples. Little difference was found between the two heating methods. The attenuation factor which has based on the dielectric constant and loss showed differences in the way the sample interacted with electromagnetic energy. The gluten was fractioned with dilute HCl to give six groups of protein. Starch appeared to have an effect on how the gluten denatured. When the fractions were characterized with SDS-PAGE it was found that each fraction contained a wide range of proteins with different molecular weights. Differences were found in the band patterns between the CV- and MW -heated samples. ^{13}C NMR also was used, which provided information on the protein and carbohydrate component of the fractions showed differences between the CV and MW heated samples, especially

  19. Novel Direct Steelmaking by Combining Microwave, Electric Arc, and Exothermal Heating Technologies

    SciTech Connect

    Dr. Xiaodi Huang; Dr. J. Y. Hwang

    2005-03-28

    Steel is a basic material broadly used by perhaps every industry and individual. It is critical to our nation's economy and national security. Unfortunately, the American steel industry is losing competitiveness in the world steel production field. There is an urgent need to develop the next generation of steelmaking technology for the American steel industry. Direct steelmaking through the combination of microwave, electric arc, and exothermal heating is a revolutionary change from current steelmaking technology. This technology can produce molten steel directly from a shippable agglomerate, consisting of iron oxide fines, powdered coal, and ground limestone. This technology is projected to eliminate many current intermediate steelmaking steps including coking, pellet sintering, blast furnace (BF) ironmaking, and basic oxygen furnace (BOF) steelmaking. This technology has the potential to (a) save up to 45% of the energy consumed by conventional steelmaking; (b) dramatically reduce the emission of CO{sub 2}, SO{sub 2}, NO{sub x}, VOCs, fine particulates, and air toxics; (c) substantially reduce waste and emission control costs; (d) greatly lower capital cost; and (e) considerably reduce steel production costs. This technology is based on the unique capability of microwaves to rapidly heat steelmaking raw materials to elevated temperature, then rapidly reduce iron oxides to metal by volumetric heating. Microwave heating, augmented with electric arc and exothermal reactions, is capable of producing molten steel. This technology has the components necessary to establish the ''future'' domestic steel industry as a technology leader with a strong economically competitive position in world markets. The project goals were to assess the utilization of a new steelmaking technology for its potential to achieve better overall energy efficiency, minimize pollutants and wastes, lower capital and operating costs, and increase the competitiveness of the U.S. steel industry. The

  20. Precipitation and Latent Heating Distributions from Satellite Passive Microwave Radiometry. Part 1; Improved Method and Uncertainties

    NASA Technical Reports Server (NTRS)

    Olson, William S.; Kummerow, Christian D.; Yang, Song; Petty, Grant W.; Tao, Wei-Kuo; Bell, Thomas L.; Braun, Scott A.; Wang, Yansen; Lang, Stephen E.; Johnson, Daniel E.; hide

    2006-01-01

    A revised Bayesian algorithm for estimating surface rain rate, convective rain proportion, and latent heating profiles from satellite-borne passive microwave radiometer observations over ocean backgrounds is described. The algorithm searches a large database of cloud-radiative model simulations to find cloud profiles that are radiatively consistent with a given set of microwave radiance measurements. The properties of these radiatively consistent profiles are then composited to obtain best estimates of the observed properties. The revised algorithm is supported by an expanded and more physically consistent database of cloud-radiative model simulations. The algorithm also features a better quantification of the convective and nonconvective contributions to total rainfall, a new geographic database, and an improved representation of background radiances in rain-free regions. Bias and random error estimates are derived from applications of the algorithm to synthetic radiance data, based upon a subset of cloud-resolving model simulations, and from the Bayesian formulation itself. Synthetic rain-rate and latent heating estimates exhibit a trend of high (low) bias for low (high) retrieved values. The Bayesian estimates of random error are propagated to represent errors at coarser time and space resolutions, based upon applications of the algorithm to TRMM Microwave Imager (TMI) data. Errors in TMI instantaneous rain-rate estimates at 0.5 -resolution range from approximately 50% at 1 mm/h to 20% at 14 mm/h. Errors in collocated spaceborne radar rain-rate estimates are roughly 50%-80% of the TMI errors at this resolution. The estimated algorithm random error in TMI rain rates at monthly, 2.5deg resolution is relatively small (less than 6% at 5 mm day.1) in comparison with the random error resulting from infrequent satellite temporal sampling (8%-35% at the same rain rate). Percentage errors resulting from sampling decrease with increasing rain rate, and sampling errors in

  1. Preparation of activated carbon from coconut shell chars in pilot-scale microwave heating equipment at 60 kW.

    PubMed

    Li, Wei; Peng, Jinhui; Zhang, Libo; Yang, Kunbin; Xia, Hongying; Zhang, Shimin; Guo, Sheng-hui

    2009-02-01

    Experiments to prepare activated carbon by microwave heating indicated that microwave energy can decrease reaction temperature, save the energy and shorten processing time remarkably compared to conventional heating, owing to its internal and volumetric heating effects. The above results were based on the laboratory-scale experiments. It is desirable to develop a pilot-scale microwave heating equipment and investigate the parameters with the aim of technological industrialization. In the present study, the components and features of the self-invented equipment were introduced. The temperature rise curves of the chars were obtained. Iodine numbers of the activated carbons all exceed the state standard of China under the following conditions: 25 kg/h charging rate, 0.42 rev/min turning rate of ceramic tube, flow rate of steam at pressure of 0.01 MPa and 40 kW microwave heating power after 60 kW pre-activation for 30 min. Pore structure of the sample obtained at a time point of 46 h, which contained BET surface area, and pore size distributions of micropores and total pores, was tested by nitrogen adsorption at 77K.

  2. Preparation of activated carbon from coconut shell chars in pilot-scale microwave heating equipment at 60 kW

    SciTech Connect

    Li Wei; Peng Jinhui Zhang Libo; Yang Kunbin; Xia Hongying; Zhang Shimin; Guo Shenghui

    2009-02-15

    Experiments to prepare activated carbon by microwave heating indicated that microwave energy can decrease reaction temperature, save the energy and shorten processing time remarkably compared to conventional heating, owing to its internal and volumetric heating effects. The above results were based on the laboratory-scale experiments. It is desirable to develop a pilot-scale microwave heating equipment and investigate the parameters with the aim of technological industrialization. In the present study, the components and features of the self-invented equipment were introduced. The temperature rise curves of the chars were obtained. Iodine numbers of the activated carbons all exceed the state standard of China under the following conditions: 25 kg/h charging rate, 0.42 rev/min turning rate of ceramic tube, flow rate of steam at pressure of 0.01 MPa and 40 kW microwave heating power after 60 kW pre-activation for 30 min. Pore structure of the sample obtained at a time point of 46 h, which contained BET surface area, and pore size distributions of micropores and total pores, was tested by nitrogen adsorption at 77 K.

  3. Coupled field analysis of heat flow in the near field of a microwave applicator for tumor ablation.

    PubMed

    Hardie, Donald; Sangster, Alan J; Cronin, Nigel J

    2006-01-01

    Microwave tumor ablation (MTA) offers a new approach for the treatment of hepatic neoplastic disease. Reliable and accurate information regarding the heat distribution inside biological tissue subjected to microwave thermal ablation is important for the efficient design of microwave applicators and for optimizing experiments, which aim to assess the effects of therapeutic treatments. Currently there are a variety of computational methods based on different vascular structures in tissue, which aim to model heat distribution during ablation. This paper presents results obtained from two such computational models for temperature distributions produced by a clinical 2.45 GHz MTA applicator immersed in unperfused ex vivo bovine liver, and compares them with measured results from a corresponding ex vivo experiment. The computational methods used to model the temperature distribution in tissue caused by the insertion of a 5.6 mm diameter "wandlike" microwave applicator are the Green's function method and the finite element method (FEM), both of which provide solutions of the heat diffusion partial differential equation. The results obtained from the coupled field simulations are shown to be in good agreement with a simplified analysis based on the bio-heat equation and with ex vivo measurements of the heat distribution produced by the clinical MTA applicator.

  4. Simulating microwave-heated open systems: tuning competitive sorption in zeolites.

    PubMed

    Santander, Julian E; Conner, W Curtis; Jobic, Hervé; Auerbach, Scott M

    2009-10-22

    We have developed a new grand canonical molecular dynamics (GCMD) algorithm to study microwave (MW) heating effects on competitive mixture sorption and have applied the method to methanol and benzene in silicalite zeolite. The new algorithm combines MW-driven molecular dynamics with grand canonical Monte Carlo (GCMC), the latter modeling adsorption/desorption processes. We established the validity of the new algorithm by benchmarking single-component isotherms for methanol and benzene in silicalite against those obtained from standard GCMC, as well as against experimental data. We simulated single-component and mixture adsorption isobars for conventional and MW-heated systems. In the case of the single-component isobars, we found that for dipolar methanol, both the MW and conventional heated isobars show similar desorption behavior, displaying comparable loadings as a function of molecular temperature. In contrast, nonpolar benzene showed no desorption upon exposure to MWs, even for relatively high field strengths. In the case of methanol/benzene mixtures, the fact that benzene is transparent to the MW field allows the selective desorption of methanol, giving rise to loading ratios not reachable through conventional heating.

  5. Effects of roasting, blanching, autoclaving, and microwave heating on antigenicity of almond (Prunus dulcis L.) proteins.

    PubMed

    Venkatachalam, M; Teuber, S S; Roux, K H; Sathe, S K

    2002-06-05

    Whole, unprocessed Nonpareil almonds were subjected to a variety of heat processing methods that included roasting (280, 300, and 320 degrees F for 20 and 30 min each; and 335 and 350 degrees F for 8, 10, and 12 min each), autoclaving (121 degrees C, 15 psi, for 5, 10, 15, 20, 25, and 30 min), blanching (100 degrees C for 1, 2, 3, 4, 5, and 10 min), and microwave heating (1, 2, and 3 min). Proteins were extracted from defatted almond flour in borate saline buffer, and immunoreactivity of the soluble proteins (normalized to 1 mg protein/mL for all samples) was determined using enzyme linked immunosorbent assay (ELISA). Antigenic stability of the almond major protein (amandin) in the heat-processed samples was determined by competitive inhibition ELISA using rabbit polyclonal antibodies raised against amandin. Processed samples were also assessed for heat stability of total antigenic proteins by sandwich ELISA using goat and rabbit polyclonal antibodies raised against unprocessed Nonpareil almond total protein extract. ELISA assays and Western blotting experiments that used both rabbit polyclonal antibodies and human IgE from pooled sera indicated antigenic stability of almond proteins when compared with that of the unprocessed counterpart.

  6. Inactivation of Salmonella Senftenberg, Salmonella Typhimurium and Salmonella Tennessee in peanut butter by 915 MHz microwave heating.

    PubMed

    Song, Won-Jae; Kang, Dong-Hyun

    2016-02-01

    This study evaluated the efficacy of a 915 MHz microwave with 3 different levels to inactivate 3 serovars of Salmonella in peanut butter. Peanut butter inoculated with Salmonella enterica serovar Senftenberg, S. enterica serovar Typhimurium and S. enterica serovar Tennessee were treated with a 915 MHz microwave with 2, 4 and 6 kW and acid and peroxide values and color changes were determined after 5 min of microwave heating. Salmonella populations were reduced with increasing treatment time and treatment power. Six kW 915 MHz microwave treatment for 5 min reduced these three Salmonella serovars by 3.24-4.26 log CFU/g. Four and two kW 915 MHz microwave processing for 5 min reduced these Salmonella serovars by 1.14-1.48 and 0.15-0.42 log CFU/g, respectively. Microwave treatment did not affect acid, peroxide, or color values of peanut butter. These results demonstrate that 915 MHz microwave processing can be used as a control method for reducing Salmonella in peanut butter without producing quality deterioration.

  7. Microwave thermal imaging: initial in vivo experience with a single heating zone.

    PubMed

    Meaney, P M; Fanning, M W; Paulsen, K D; Lit, D; Pendergrass, S A; Fang, Q; Moodie, K L

    2003-01-01

    The deployment of hyperthermia as a routine adjuvant to radiation or chemotherapy is limited largely by the inability to devise treatment plans which can be monitored through temperature distribution feedback during therapy. A non-invasive microwave tomographic thermal imaging system is currently being developed which has previously exhibited excellent correlation between the recovered electrical conductivity of a heated zone and its actual temperature change during phantom studies. To extend the validation of this approach in vivo, the imaging system has been re-configured for small animal experiments to operate within the bore of a CT scanner for anatomical and thermometry registration. A series of 5-7 day old pigs have been imaged during hyperthermia with a monopole antenna array submerged in a saline tank where a small plastic tube surgically inserted the length of the abdomen has been used to create a zone of heated saline at pre-selected temperatures. Tomographic microwave data over the frequency range of 300-1000 MHz of the pig abdomen in the plane perpendicular to the torso is collected at regular intervals after the tube saline temperatures have settled to the desired settings. Images are reconstructed over a range of operating frequencies. The tube location is clearly visible and the recovered saline conductivity varies linearly with the controlled temperature values. Difference images utilizing the baseline state prior to heating reinforces the linear relationship between temperature and imaged saline conductivity. Demonstration of in vivo temperature recovery and correlation with an independent monitoring device is an important milestone prior to clinical integration of this non-invasive imaging system with a thermal therapy device.

  8. Conventional heating vs. microwave sludge pretreatment comparison under identical heating/cooling profiles for thermophilic advanced anaerobic digestion.

    PubMed

    Hosseini Koupaie, E; Eskicioglu, C

    2016-07-01

    This research evaluates whether there is any advantage of selecting one of the thermal methods of sludge pretreatment, conventional heating (CH) and microwave hydrolysis (MW), over another to enhance municipal sludge disintegration and performance of thermophilic anaerobic digestion (AD). For this purpose, a custom-built CH system simulating MW hydrolysis under identical heating and cooling profiles was used. The effects of three main pretreatment parameters including pretreatment method (CH and MW), heating ramp rate (3, 6 and 11°C/min) and final temperature (80, 120 and 160°C) on sludge solubilization and performance of thermophilic batch AD were evaluated. The effects of CH and MW hydrolysis were observed to be similar for sludge disintegration and digester performance (p-value>0.05), while the effects of final temperature and heating ramp rate were proven to be different (p-value<0.05). According to the results, it is essential to apply MW and CH pretreatments under identical experimental condition for an unbiased comparison which supports the findings of the author's earlier study under mesophilic condition. Failing to address this issue explains the significant inconsistency observed among the findings of the previous CH vs. MW comparison studies that were unable to implement identical thermal profiles (between CH and MW) during sludge pretreatment. In comparison with mesophilic AD, thermophilic AD revealed lower biodegradation rate constant at the highest pretreatment temperature tested (160°C), suggesting its higher sensitivity to the inhibitory effects of thermal pretreatment at the elevated temperatures. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Passive and Active Microwave Remote Sensing of Precipitation and Latent Heating Distributions in the Tropics from TRMM

    NASA Technical Reports Server (NTRS)

    Olson, William S.; Kummerow, Christian D.; Yang, Song; Haddad, Ziad S.; Tao, Wei-Kuo; Wang, Yansen; Lang, Stephen E.; Braun, Scott A.; Chiu, Christine; Wang, Jian-Jian

    2002-01-01

    Passive and active microwave remote sensing data are analyzed to identify signatures of precipitation and vertical motion in tropical convection. A database of cloud/radiative model simulations is used to quantify surface rain rates and latent heating profiles that are consistent with these signatures. At satellite footprint-scale (approximately 10 km), rain rate and latent heating estimates are subject to significant random errors, but by averaging the estimates in space and time, random errors are substantially reduced, Bias errors have been minimized by improving the microphysics in the supporting cloud/radiative model simulations, and by imposing a consistent definition of remotely-sensed and model-simulated convective/stratiform rain coverage. Remotely-sensed precipitation and latent heating distributions in the tropics are derived from Tropical Rainfall Measuring Mission (TRMM) and Special Sensor Microwave/ Imager (SSM/ I) sensor data. The prototype Version 6 TRMM passive microwave algorithm typically yields average heating profiles with maxima between 6 and 7 km altitude for organized mesoscale convective systems. Retrieved heating profiles for individual convective systems are compared to coincident estimates based upon a combination of dual-Doppler radar and rawinsonde data. Also, large-scale latent heating distributions are compared to estimates derived from a simpler technique that utilizes observations of surface rain rate and stratiform rain proportion to infer vertical heating structure. Results of these tests will be presented at the conference.

  10. Passive and Active Microwave Remote Sensing of Precipitation and Latent Heating Distributions in the Tropics from TRMM

    NASA Technical Reports Server (NTRS)

    Olson, William S.; Kummerow, Christian D.; Yang, Song; Haddad, Ziad S.; Tao, Wei-Kuo; Wang, Yansen; Lang, Stephen E.; Braun, Scott A.; Chiu, Christine; Wang, Jian-Jian

    2002-01-01

    Passive and active microwave remote sensing data are analyzed to identify signatures of precipitation and vertical motion in tropical convection. A database of cloud/radiative model simulations is used to quantify surface rain rates and latent heating profiles that are consistent with these signatures. At satellite footprint-scale (approximately 10 km), rain rate and latent heating estimates are subject to significant random errors, but by averaging the estimates in space and time, random errors are substantially reduced, Bias errors have been minimized by improving the microphysics in the supporting cloud/radiative model simulations, and by imposing a consistent definition of remotely-sensed and model-simulated convective/stratiform rain coverage. Remotely-sensed precipitation and latent heating distributions in the tropics are derived from Tropical Rainfall Measuring Mission (TRMM) and Special Sensor Microwave/ Imager (SSM/ I) sensor data. The prototype Version 6 TRMM passive microwave algorithm typically yields average heating profiles with maxima between 6 and 7 km altitude for organized mesoscale convective systems. Retrieved heating profiles for individual convective systems are compared to coincident estimates based upon a combination of dual-Doppler radar and rawinsonde data. Also, large-scale latent heating distributions are compared to estimates derived from a simpler technique that utilizes observations of surface rain rate and stratiform rain proportion to infer vertical heating structure. Results of these tests will be presented at the conference.

  11. Stability of Continental Lithosphere based on Analogue Experiments with Microwave Induced Internal Heating

    NASA Astrophysics Data System (ADS)

    Fourel, Loic; Limare, Angela; Surducan, Emanoil; Surducan, Vasile; Neamtu, Camelia; Vilella, Kenny; Farnetani, Cinzia; Kaminski, Edouard; Jaupart, Claude

    2015-04-01

    Continental lithosphere is usually depicted as the upper conductive layer of the Earth. Its formation is achieved through melt depletion that generates a residue that is less dense and more viscous than the underlying convecting mantle. As it is cooled from above, continental lithosphere can develop its own convective currents and may become unstable depending on its thickness and density contrast with the mantle. But chemical differentiation due to mantle magmatism also enriches continental lithosphere in heat producing elements. According to present estimates, the Earth's mantle may have lost as much as half of its radioactive elements in favour of continental crust and this stratified redistribution of heat sources has two main effects. First, mantle convection vigor decreases and becomes increasingly sensitive to heat supply from the core. Second, localized heat production at the top surface increases the continental insulating effects and competes against lithospheric instabilities. In the present study, we focus on the later and we determine which amount of internal heating is required to keep the lithosphere stable for a given rate of cooling from the top. The physics underlying instability triggering corresponds to the problem of a two differentially heated layered system cooled from above, where the top layer is less dense and more viscous than the bottom one, representative of the lithosphere-mantle system. Few studies have been devoted to the intrinsic characteristics of this layered type of convection. Here, we present a state of the art laboratory setup to generate internal heating in controlled conditions based on microwave (MW) absorption. The volumetric heat source can be localized in space and its intensity can be varied in time. Our tank prototype has horizontal dimensions of 30 cm x 30 cm and 5 cm height. A uniform and constant temperature is maintained at the upper boundary by an aluminium heat exchanger and adiabatic conditions are imposed at

  12. Subtle Mitsunobu couplings under super-heating: the role of high-throughput continuous flow and microwave strategies.

    PubMed

    Manvar, Atul; Shah, Anamik

    2014-11-07

    Non-conventional heating techniques, high-throughput microwave-assisted synthesis and continuous flow penetrate almost every scientific field. Mitsunobu coupling is a ubiquitous choice for the dehydrative redox condensation of primary or secondary alcohols with (pro)nucleophiles. The aim of this review is to showcase the ease of subtle Mitsunobu coupling under super-heating. Surprisingly, this strategy is rather non-trivial; considering the sensitivity of reagents, Mitsunobu chemistry is typically performed at lower temperatures or under ambient conditions. In view of the absence of any previous work focusing on this topic, the current review considers the utility of super-heating in fragile Mitsunobu reactions. Therefore, we anticipate that this review will also bridge some of the apparent gaps in the extant literature by specifically describing the advances made by non-conventional heating assisted by microwave or continuous flow in one of the most powerful stereochemical transformations.

  13. Poly(4-vinylphenol) gate insulator with cross-linking using a rapid low-power microwave induction heating scheme for organic thin-film-transistors

    NASA Astrophysics Data System (ADS)

    Fan, Ching-Lin; Shang, Ming-Chi; Hsia, Mao-Yuan; Wang, Shea-Jue; Huang, Bohr-Ran; Lee, Win-Der

    2016-03-01

    A Microwave-Induction Heating (MIH) scheme is proposed for the poly(4-vinylphenol) (PVP) gate insulator cross-linking process to replace the traditional oven heating cross-linking process. The cross-linking time is significantly decreased from 1 h to 5 min by heating the metal below the PVP layer using microwave irradiation. The necessary microwave power was substantially reduced to about 50 W by decreasing the chamber pressure. The MIH scheme is a good candidate to replace traditional thermal heating for cross-linking of PVP as the gate insulator for organic thin-film-transistors.

  14. Dual-slot antennas for microwave tissue heating: parametric design analysis and experimental validation.

    PubMed

    Brace, Christopher L

    2011-07-01

    Design and validate an efficient dual-slot coaxial microwave ablation antenna that produces an approximately spherical heating pattern to match the shape of most abdominal and pulmonary tumor targets. A dual-slot antenna geometry was utilized for this study. Permutations of the antenna geometry using proximal and distal slot widths from 1 to 10 mm separated by 1-20 mm were analyzed using finite-element electromagnetic simulations. From this series, the most optimal antenna geometry was selected using a two-term sigmoidal objective function to minimize antenna reflection coefficient and maximize the diameter-to-length aspect ratio of heat generation. Sensitivities to variations in tissue properties and insertion depth were also evaluated in numerical models. The most optimal dual-slot geometry of the parametric analysis was then fabricated from semirigid coaxial cable. Antenna reflection coefficients at various insertion depths were recorded in ex vivo bovine livers and compared to numerical results. Ablation zones were then created by applying 50 W for 2-10 min in simulations and ex vivo livers. Mean zone diameter, length, aspect ratio, and reflection coefficients before and after heating were then compared to a conventional monopole antenna using ANOVA with post-hoc t-tests. Statistical significance was indicated for P <0.05. Antenna performance was highly sensitive to dual-slot geometry. The best-performing designs utilized a proximal slot width of 1 mm, distal slot width of 4 mm +/- 1 mm and separation of 8 mm +/- 1 mm. These designs were characterized by an active choking mechanism that focused heating to the distal tip of the antenna. A dual-band resonance was observed in the most optimal design, with a minimum reflection coefficient of -20.9 dB at 2.45 and 1.25 GHz. Total operating bandwidth was greater than 1 GHz, but the desired heating pattern was achieved only near 2.45 GHz. As a result, antenna performance was robust to changes in insertion depth and

  15. Survival of Listeria monocytogenes and Salmonella spp. on catfish exposed to microwave heating in a continuous mode

    USDA-ARS?s Scientific Manuscript database

    Microwave (MW) heating using continuous output may provide better and consistent cooking for foods. Currently, household units with a build-in inverter device are available in which the output is continuous vs. the traditional on-off mode. With an inverter, these MW ovens may provide consistent he...

  16. Electromagnetic property of SiO2-coated carbonyl iron/polyimide composites as heat resistant microwave absorbing materials

    NASA Astrophysics Data System (ADS)

    Wang, Hongyu; Zhu, Dongmei; Zhou, Wancheng; Luo, Fa

    2015-02-01

    Heat resistant microwave absorbing materials were prepared by compression molding method, using polyimide resin as matrix and SiO2 coated carbonyl iron (CI) as filler. The SiO2 coated CI particles were prepared by Stober process. The microwave absorbing properties and the effect of heat treatment on the electromagnetic properties of SiO2 coated CI/polyimide composites were investigated. When the content of SiO2 coated CI is 60 wt%, the value of minimum reflection loss decreases from -25 dB to -33 dB with the thickness increases from 1.5 mm to 2.1 mm. According to the thermal-gravimetric analyses (TGA) curves, the polyimide matrix can be used at 300 °C for long time. The complex permittivity of the composites slightly increases while the complex permeability almost keeps constant after heat treatment at 300 °C for 10 h, which indicating that the composites can be used at elevated temperature as microwave absorbing materials at the same time have good heat resistance and microwave absorption.

  17. Effects of ZnO nanoparticles and microwave heating on the sterilization and product quality of vacuum-packaged Caixin.

    PubMed

    Liu, Qian; Zhang, Min; Fang, Zhong-xiang; Rong, Xiao-hong

    2014-09-01

    The sterilization of vacuum-packaged Caixin (Brassica chinensis L.), which is a green-leafy vegetable and also a low-acid food, remains a difficult problem. In this study, effects of ZnO nanoparticles and microwave heating on the sterilization and product quality of vacuum-packaged Caixin were investigated. Addition of ZnO nanoparticle suspension at 0.01-0.02 g kg(-1) reduced the number of bacterial colonies. The antibacterial activity was enhanced with the increased amount of ZnO nanoparticles. Microwave heating (915 and 2450 MHz) was used to sterilize Caixin samples. Samples had good product quality (better greenness, chroma and hue angle values, lower browning index and acceptable texture) and the lowest total colony number under the microwave heating condition of 400 W 150 s (2450 MHz). The best sterilization condition was observed under 2450 MHz microwave (400 W 150 s) heating combined with 0.02 g kg(-1) ZnO nanoparticle addition, which led to a total colony number of <1 log CFU g(-1) in Caixin samples within 7 days. © 2014 Society of Chemical Industry.

  18. Dielectric-loaded coaxial-slot antenna for interstitial microwave hyperthermia: longitudinal control of heating patterns.

    PubMed

    Hamada, L; Saito, K; Yoshimura, H; Ito, K

    2000-01-01

    In this paper, the microwave interstitial antenna with the dielectric load in part near the tip is introduced to realize the tip-heating and to improve the dependence of the heating patterns on the insertion depth. Numerical simulations using the Finite Difference Time Domain (FDTD) method have been conducted at the frequency of 915 MHz for four different configurations of the coaxial-slot antenna inserted into a catheter: the media between the antenna and the catheter are (a) no, (b) a thin air layer, (c) a thin dielectric layer, and (d) a thin air layer and a dielectric load in part near the tip. The diameter of the antenna including the catheter is sufficiently small for minimally invasive therapy. Comparison of the SARs for the four configurations makes it clear that the dielectric-loaded antenna can realize the best tip-heating and suppress the hot spot near the surface of the human body. Dependence of the SAR distributions on the insertion depth of the antenna has also been examined. It is found from the investigation that the dielectric-loaded antenna has little dependence on the insertion depth.

  19. Effects of pulse-modulated microwave radiation and conventional heating on sperm production

    SciTech Connect

    Lebovitz, R.M.; Johnson, L.; Samson, W.K.

    1987-01-01

    The effects on testicular function of pulse-modulated microwave radiation (PM MWR, 1.3 GHz) and of conventional heating were studied in the rat. Anesthetized adult males (Sprague-Dawley, 400-500 g) were treated then killed at specific intervals with respect to the 13-day cycle of the seminiferous epithelium. PM MWR at 7.7 mW/g (90 min) yielded a modest decline in daily sperm production (DSP) that derived primarily from effects on primary spermatocytes. PM MWR at 4.2 mW/g was ineffective. The mean intratesticular temperature during the former reached 40 degrees C and did not exceed 38 degrees C during the latter. MWR considerably in excess of 7.7 mW/g yielded decrements in virtually all germ cell types, with primary spermatocytes again being most markedly affected. Using conventional heating, intratesticular temperatures in excess of 39 degrees C for 60 min were required for significant decrements in DSP. Levels of circulating follicle-stimulating hormone and of leutinizing hormone were resistant to either treatment. We conclude that the damage threshold and the differential sensitivity of immature germ cells to PM MWR can be adequately explained by the consequent macroscopic heating.

  20. Influence of the dielectric property on microwave oven heating patterns: application to food materials.

    PubMed

    Peyre, F; Datta, A; Seyler, C

    1997-01-01

    Patterns of power absorption in a microwave oven for a range of dielectric properties of relevance to food processing were investigated. The governing Maxwell's equations with boundary conditions and a TE10 excitation were solved using a finite element method. Food properties were varied from values at their frozen state to values at high temperatures, as would be typical in a thawing process. For low-loss materials such as frozen foods, the high quality factor makes the heating significantly higher only when the size and shape of the load permit a dielectric cavity resonance in the load. Otherwise, the heating pattern will follow the modal electric field pattern of the oven. For moderate loss materials, the patterns will come from the modes of the dielectric cavity. The bandwidths of these modes are larger than the low-loss situation and their overlap results in a heating pattern that is somewhat more uniform. For high-loss materials, the concept of modes is no longer useful as the very large number of modes strongly overlap. The rapidly decaying field and power loss in the high-loss material can probably be characterized as an exponential decay.

  1. Stabilization of Titanium Dioxide Nanoparticles at the Surface of Carbon Nanomaterials Promoted by Microwave Heating.

    PubMed

    Zhang, Rui; Santangelo, Saveria; Fazio, Enza; Neri, Fortunato; D'Arienzo, Massimiliano; Morazzoni, Franca; Zhang, Yihe; Pinna, Nicola; Russo, Patrícia A

    2015-10-12

    TiO2 is frequently combined with carbon materials, such as reduced graphene oxide (RGO), to produce composites with improved properties, for example for photocatalytic applications. It is shown that heating conditions significantly affect the interface and photocatalytic properties of TiO2 @C, and that microwave irradiation can be advantageous for the synthesis of carbon-based materials. Composites of TiO2 with RGO or amorphous carbon were prepared from reaction of titanium isopropoxide with benzyl alcohol. During the synthesis of the TiO2 nanoparticles, the carbon is involved in reactions that lead to the covalent attachment of the oxide, the extent of which depends on the carbon characteristics, heating rate, and mechanism. TiO2 is more efficiently stabilized at the surface of RGO than amorphous carbon. Rapid heating of the reaction mixture results in a stronger coupling between the nanoparticles and carbon, more uniform coatings, and smaller particles with narrower size distributions. The more efficient attachment of the oxide leads to better photocatalytic performance. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Analysis of the temperature and stress distributions in ceramic window materials subjected to microwave heating

    SciTech Connect

    Ferber, M.K.; Kimrey, H.D.; Becher, P.F.

    1983-07-01

    The temperature and stress and distributions generated in ceramic materials currently employed in microwave gyrotron tube windows were determined for a variety of operating conditions. Both edge- and face-cooled windows of either polycrystalline BeO or polycrystalline Al/sub 2/O/sub 3/ were considered. The actual analysis involved three steps. First, a computer program was used to determine the electric field distribution within the window at a given power level and frequency (TE/sub 02/ wave propagation assumed). This program was capable of describing both the radial and axial dependence of the electric field. The effects of multiple internal reflections at the various dielectric interfaces were also accounted for. Secondly, the field distribution was used to derive an expression for the heat generated per unit volume per unit time within the window due to dieletric losses. A generalized heat conduction computer code was then used to compute the temperature distribution based on the heat generation function. Third, the stresses were determined from the temperature profiles using analytical expression or a finite-element computer program. Steady-state temperature and stress profiles were computed for the face-cooled and edge-cooled windows.

  3. Microwave Heating, Isothermal Sintering, and Mechanical Properties of Powder Metallurgy Titanium and Titanium Alloys

    NASA Astrophysics Data System (ADS)

    Luo, S. D.; Guan, C. L.; Yang, Y. F.; Schaffer, G. B.; Qian, M.

    2013-04-01

    This article presents a detailed assessment of microwave (MW) heating, isothermal sintering, and the resulting tensile properties of commercially pure Ti (CP-Ti), Ti-6Al-4V, and Ti-10V-2Fe-3Al (wt pct), by comparison with those fabricated by conventional vacuum sintering. The potential of MW sintering for titanium fabrication is evaluated accordingly. Pure MW radiation is capable of heating titanium powder to ≥1573 K (1300 °C), but the heating response is erratic and difficult to reproduce. In contrast, the use of SiC MW susceptors ensures rapid, consistent, and controllable MW heating of titanium powder. MW sintering can consolidate CP-Ti and Ti alloys compacted from -100 mesh hydride-dehydride (HDH) Ti powder to ~95.0 pct theoretical density (TD) at 1573 K (1300 °C), but no accelerated isothermal sintering has been observed over conventional practice. Significant interstitial contamination occurred from the Al2O3-SiC insulation-susceptor package, despite the high vacuum used (≤4.0 × 10-3 Pa). This leads to erratic mechanical properties including poor tensile ductility. The use of Ti sponge as impurity (O, N, C, and Si) absorbers can effectively eliminate this problem and ensure good-to-excellent tensile properties for MW-sintered CP-Ti, Ti-10V-2Fe-3Al, and Ti-6Al-4V. The mechanisms behind various observations are discussed. The prime benefit of MW sintering of Ti powder is rapid heating. MW sintering of Ti powder is suitable for the fabrication of small titanium parts or titanium preforms for subsequent thermomechanical processing.

  4. Feasibility study of microwave electron heating on the C-2 field-reversed configuration device

    NASA Astrophysics Data System (ADS)

    Yang, Xiaokang; Koehn, Alf; Petrov, Yuri; Ceccherini, Francesco; Dettrick, Sean; Binderbauer, Michl

    2015-12-01

    Different microwave heating scenarios for the C-2 plasmas have been investigated recently with use of both the Genray ray-racing code and the IPF-FDMC full-wave code, and the study was focused on the excitation of the electron Bernstein wave (EBW) with O-mode launch. For a given antenna position on C-2 and the fixed 2D plasma density and equilibrium field profiles, simulations have been done for six selected frequencies (2.45 GHz, 5 GHz, 8 GHz, 18 GHz, 28 GHz, and 50 GHz). Launch angles have been optimized for each case in order to achieve high coupling efficiencies to the EBW by the O-X-B mode conversion process and high power deposition. Results show that among those six frequencies, the case of 8 GHz is the most promising scenario, which has both high mode conversion efficiency (90%) and the relatively deeper power deposition.

  5. Uniform staining of Cyclospora oocysts in fecal smears by a modified safranin technique with microwave heating.

    PubMed

    Visvesvara, G S; Moura, H; Kovacs-Nace, E; Wallace, S; Eberhard, M L

    1997-03-01

    Cyclospora, a coccidian protist, is increasingly being identified as an important, newly emerging parasite that causes diarrhea, flatulence, fatigue, and abdominal pain leading to weight loss in immunocompetent persons with or without a recent travel history as well as in patients with AIDS. Modified Kinyoun's acid-fast stain is the most commonly used stain to identify the oocyst of this parasite in fecal smears. Oocysts of Cyclospora stain variably by the modified acid-fast procedure, resulting in the possible misidentification of this parasite. We examined fecal smears stained by six different procedures that included Giemsa, trichrome, chromotrope, Gram-chromotrope, acid-fast, and safranin stains. We report on safranin-based stain that uniformly stains oocysts of Cyclospora a brilliant reddish orange, provided that the fecal smears are heated in a microwave oven prior to staining. This staining procedure, besides being superior to acid-fast staining, is fast, reliable, and easy to perform in most clinical laboratories.

  6. Application of carbon nanocatalysts in upgrading heavy crude oil assisted with microwave heating.

    PubMed

    Li, Kewen; Hou, Binchi; Wang, Lei; Cui, Yi

    2014-06-11

    Heavy crude oil can be upgraded to lighter oil using several techniques. However, current methods usually require high temperatures, long reaction duration, and cause serious environmental pollution. This study shows that by using carbon nanocatalysts, heavy crude oil can be efficiently upgraded to lighter oil at a relatively low temperature of about 150 °C. The temperature of crude oil was increased by microwave heating. The technique proposed in this study has the following advantages: (1) great viscosity reduction ratio over 96%, (2) short reaction time (less than 1 h), (3) low required temperature, and (4) long viscosity regression time. Because of these advantages, upgrading heavy crude oil to light oil can be cheaper and more environment-friendly.

  7. Continuous synthesis of monodispersed silver nanoparticles using a homogeneous heating microwave reactor system.

    PubMed

    Nishioka, Masateru; Miyakawa, Masato; Kataoka, Haruki; Koda, Hidekazu; Sato, Koichi; Suzuki, Toshishige M

    2011-06-01

    Continuous synthesis of silver nanoparticles based on a polyol process was conducted using a microwave-assisted flow reactor installed in a cylindrical resonance cavity. Silver nitrate (AgNO(3)) and poly(N-vinylpyrrolidone) (PVP) dissolved in ethylene glycol were used respectively as a silver metal precursor and as a capping agent of nanoparticles. Ethylene glycol worked as the solvent and simultaneously as the reductant. Silver nanoparticles of narrow size distributions were synthesized steadily for 5 h, maintaining almost constant yield (>93%) and quality. The reaction was achieved within 2.8 s of residence time, although nanoparticles were not formed under this flow rate by conventional heating. A narrower particle size distribution was realized by the increased flow rate of the reaction solution. Nanoparticles of 9.8 nm average size with a standard deviation of 0.9 nm were synthesized at the rate of 100 ml h(-l).

  8. No major differences found between the effects of microwave-based and conventional heat treatment methods on two different liquid foods.

    PubMed

    Géczi, Gábor; Horváth, Márk; Kaszab, Tímea; Alemany, Gonzalo Garnacho

    2013-01-01

    Extension of shelf life and preservation of products are both very important for the food industry. However, just as with other processes, speed and higher manufacturing performance are also beneficial. Although microwave heating is utilized in a number of industrial processes, there are many unanswered questions about its effects on foods. Here we analyze whether the effects of microwave heating with continuous flow are equivalent to those of traditional heat transfer methods. In our study, the effects of heating of liquid foods by conventional and continuous flow microwave heating were studied. Among other properties, we compared the stability of the liquid foods between the two heat treatments. Our goal was to determine whether the continuous flow microwave heating and the conventional heating methods have the same effects on the liquid foods, and, therefore, whether microwave heat treatment can effectively replace conventional heat treatments. We have compared the colour, separation phenomena of the samples treated by different methods. For milk, we also monitored the total viable cell count, for orange juice, vitamin C contents in addition to the taste of the product by sensory analysis. The majority of the results indicate that the circulating coil microwave method used here is equivalent to the conventional heating method based on thermal conduction and convection. However, some results in the analysis of the milk samples show clear differences between heat transfer methods. According to our results, the colour parameters (lightness, red-green and blue-yellow values) of the microwave treated samples differed not only from the untreated control, but also from the traditional heat treated samples. The differences are visually undetectable, however, they become evident through analytical measurement with spectrophotometer. This finding suggests that besides thermal effects, microwave-based food treatment can alter product properties in other ways as well.

  9. No Major Differences Found between the Effects of Microwave-Based and Conventional Heat Treatment Methods on Two Different Liquid Foods

    PubMed Central

    Géczi, Gábor; Horváth, Márk; Kaszab, Tímea; Alemany, Gonzalo Garnacho

    2013-01-01

    Extension of shelf life and preservation of products are both very important for the food industry. However, just as with other processes, speed and higher manufacturing performance are also beneficial. Although microwave heating is utilized in a number of industrial processes, there are many unanswered questions about its effects on foods. Here we analyze whether the effects of microwave heating with continuous flow are equivalent to those of traditional heat transfer methods. In our study, the effects of heating of liquid foods by conventional and continuous flow microwave heating were studied. Among other properties, we compared the stability of the liquid foods between the two heat treatments. Our goal was to determine whether the continuous flow microwave heating and the conventional heating methods have the same effects on the liquid foods, and, therefore, whether microwave heat treatment can effectively replace conventional heat treatments. We have compared the colour, separation phenomena of the samples treated by different methods. For milk, we also monitored the total viable cell count, for orange juice, vitamin C contents in addition to the taste of the product by sensory analysis. The majority of the results indicate that the circulating coil microwave method used here is equivalent to the conventional heating method based on thermal conduction and convection. However, some results in the analysis of the milk samples show clear differences between heat transfer methods. According to our results, the colour parameters (lightness, red-green and blue-yellow values) of the microwave treated samples differed not only from the untreated control, but also from the traditional heat treated samples. The differences are visually undetectable, however, they become evident through analytical measurement with spectrophotometer. This finding suggests that besides thermal effects, microwave-based food treatment can alter product properties in other ways as well. PMID

  10. Comparison of microwaves to fluidized sand baths for heating tubular reactors for hydrothermal and dilute acid batch pretreatment of corn stover.

    PubMed

    Shi, Jian; Pu, Yunqiao; Yang, Bin; Ragauskas, Arthur; Wyman, Charles E

    2011-05-01

    Heating of batch tubular reactors with fluidized sand baths and with microwaves resulted in distinctive sugar yield profiles from pretreatment and subsequent enzymatic hydrolysis of corn stover at the same time, temperature, and dilute sulfuric acid concentration combinations and hydrothermal pretreatment conditions. Microwave heated pretreatment led to faster xylan, lignin, and acetyl removal as well as earlier xylan degradation than sand baths, but maximum sugar recoveries were similar. Solid state CP/MAS NMR revealed that microwave heating was more effective in altering cellulose structural features especially in breakdown of amorphous regions of corn stover than sand bath heating. Enzymatic hydrolysis of pretreated corn stover was improved by microwave heating compared to sand bath heating. Mechanisms were proposed to explain the differences in results for the two systems and provide new insights into pretreatment that can help advance this technology. Copyright © 2011 Elsevier Ltd. All rights reserved.

  11. Microwave ablation of the liver: a description of lesion evolution over time and an investigation of the heat sink effect.

    PubMed

    Bhardwaj, N; Dormer, J; Ahmad, F; Strickland, A D; Gravante, G; West, K; Dennison, A R; Lloyd, D M

    2011-12-01

    Microwave ablation has been successfully used to treat unresectable liver tumours for many years. However, despite its widespread use, there seems to be a relative paucity of experimental data regarding lesion evolution and the effects of any surrounding vasculature on ablation morphology. The aim of this study was to investigate the principal pathological changes in the liver following microwave ablation, in particular the heat sink effect. In addition we carefully reviewed the available literature to provide an overview of all relevant pathological studies. Microwave ablation was carried out on male rats at various distances from the hilum. Histological (H&E) and immunocytochemical (caspase 3) analyses of the lesion were performed at various time points; 0, 4, 24, 48  hours, 2 weeks and 1 month. A literature review was carried out using Medline, Embase and the Cochrane database to identify all relevant histological studies. The lesion underwent complete coagulative necrosis and was extremely regular at the ablation edge with no evidence of any influence from surrounding blood vessels at all time points. H&E and caspase 3 results were consistent and microwave caused little collateral damage outside the intended ablation zone. This study suggests that microwave ablation is extremely concise and is minimally affected by the heat sink effect. Comparative investigations with other treatment modalities are required.

  12. Microwave heating of fluid/solid layers: A study of hydrodynamic stability and melting front propagation

    NASA Astrophysics Data System (ADS)

    Gilchrist, John Joseph

    In this work we study the effects of externally induced heating on the dynamics of fluid layers, and materials composed of two phases separated by a thermally driven moving front. One novel aspect of our study, is in the nature of the external source which is provided by the action of microwaves acting on dielectric materials. The main challenge is to model and solve systems of differential equations which couple fluid dynamical motions (the Navier-Stokes equations for non-isothermal flows) and electromagnetic wave propagation (governed by Maxwell's equations). When an electromagnetic wave impinges on a material, energy is generated within the material due to dipolar and ohmic heating. In the first part of the thesis, we consider hydrodynamic instabilities of such systems with particular emphasis on conditions for onset of convection. This is achieved by solving the linear stability equations in order to identify parameter values which produce instability. The analysis and subsequent numerical solutions are carried out both for materials with constant dielectric attributes (in such cases the electric field equations decouple and they can be solved in closed form), and materials with temperature dependent conductivities, dielectric permittivities and dielectric loss factors. In the latter case we incorporate known data for water or ethanol into our numerical solutions. Our solutions provide a complete picture of onset conditions as a function of input power levels and microwave frequency (or equivalently fluid layer thickness). In addition, in the case of water, the flow is found to be more stable for constant attributes as compared with temperature dependent attributes; that is, a higher power is required to set the fluid layer into convective motions in the latter case. We have also established that onset is obtained at power levels well below those needed to cause thermal runaway and consequently boiling of the water layer, for instance. Our results also identify

  13. The effect of microwave power and heating time pretreatment on biogas production from fresh and dried water hyacinth (Eichhornia crassipes)

    NASA Astrophysics Data System (ADS)

    Sumardiono, Siswo; Budiyono, Mardiani, Dini Tri

    2015-12-01

    The objective of this research was to study the effect of microwave pretreatment of fresh and dried water hyacinth on biogas production. The variations of microwave power levels are 240; 400; 560 and 800 W. The variations of microwave heating time are 5; 7 and 9 min. The unpretreated fresh and dried water hyacinth are used as control. The result of research showed that almost all pretreated water hyacinth produced biogas were higher compare tounpretreated water hyacinth. The maximum of biogas production from fresh and dried water hyacinthwere obtained at 560 W for 7 min and 400 W for 7 min of microwave pretreatment. In this condition, pretreated fresh and dried water hyacinth resulted biogas production of 75,12 and 53,06 mL/g TS, respectively. The unpretreated fresh and dried water hyacinth produced biogas of 37,56 and 33,56 mL/g TS, respectively. The microwave pretreatment of water hyacinth improved biogas production. Microwave pretreatment had a positive impact on anaerobic biodegradability of water hyacinth.

  14. Below and above boiling point comparison of microwave irradiation and conductive heating for municipal sludge digestion under identical heating/cooling profiles.

    PubMed

    Hosseini Koupaie, E; Eskicioglu, C

    2015-01-01

    This research provides a comprehensive comparison between microwave (MW) and conductive heating (CH) sludge pretreatments under identical heating/cooling profiles at below and above boiling point temperatures. Previous comparison studies were constrained to an uncontrolled or a single heating rate due to lack of a CH equipment simulating MW under identical thermal profiles. In this research, a novel custom-built pressure-sealed vessel which could simulate MW pretreatment under identical heating/cooling profiles was used for CH pretreatment. No statistically significant difference was proven between MW and CH pretreatments in terms of sludge solubilization, anaerobic biogas yield and organics biodegradation rate (p-value>0.05), while statistically significant effects of temperature and heating rate were observed (p-value<0.05). These results explain the contradictory results of previous studies in which only the final temperature (not heating/cooling rates) was controlled. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Microwave blanching and drying characteristics of Centella asiatica (L.) urban leaves using tray and heat pump-assisted dehumidified drying.

    PubMed

    Trirattanapikul, W; Phoungchandang, S

    2014-12-01

    The appropriate stage of maturity of Centella asiatica (L.) Urban leaves was investigated. Mature leaves with large diameter contained high total phenolics and % inhibition. Microwave blanching for 30 s retained the highest total phenolics and the microwave blanching for 30 s and 45 s retained the highest % inhibition. Modified Henderson and Modified Chung-Pfost models showed the best fit to both fresh and blanched leaves for equilibrium moisture content, Xe = f(RHe, T) and equilibrium relative humidity, RHe = f(Xe, T), respectively. The Modified Page model was the most effective model in describing the leaf drying. All drying was in the falling rate period. The drying constant was related to drying air temperature using the Arrhenius model. Effective moisture diffusivities increased with increasing temperature and blanching treatments as well as dehumidification by heat pump-assisted dehumidified dryer. The heat pump-assited dehumidified drying incorporated by the microwave blanching could reduce the drying time at 40 °C by 31.2 % and increase % inhibition by 6.1 %. Quality evaluation by total phenolics, % inhibition and rehydration ratio showed the best quality for C. asiatica leaves pretreated by microwave blanching and dried at 40 °C in heat pump-assisted dehumidified dryer.

  16. Chlorophylls and carotenoids of kiwifruit puree are affected similarly or less by microwave than by conventional heat processing and storage.

    PubMed

    Benlloch-Tinoco, María; Kaulmann, Anouk; Corte-Real, Joana; Rodrigo, Dolores; Martínez-Navarrete, Nuria; Bohn, Torsten

    2015-11-15

    The impact of microwave (1000 W - 340 s) and conventional heat (97 °C - 30s) pasteurisation and storage (4, 10, 22 °C for up to 63 d) on total and individual carotenoids and chlorophylls in kiwifruit puree was evaluated. Bioaccessibility of carotenoids, before and after pasteurisation and storage, was also studied. Microwaves and conventional heating led to marked changes in the chlorophyll (42-100% losses) and carotenoid (62-91% losses) content. First- and second-order kinetics appropriately explained the degradation of total carotenoids and chlorophylls over time, respectively. Pasteurised samples showed significantly (p < 0.05) enhanced stability of these pigments, with microwaves (k = 0.007-0.031100 g mg(-1) day(-1) at 4-22 °C) promoting chlorophyll stability to a greater extent than conventional heating (k = 0.0015-0.034100 g mg(-1) day(-1) at 4-22 °C). Bioaccessibility of carotenoids remained (p < 0.05) unaffected by processing and storage. These results highlighted that the pigment composition of microwaved kiwifruit was more similar to that of the fresh fruit and better preserved during storage.

  17. Efficiency of Artemia cysts removal as a model invasive spore using a continuous microwave system with heat recovery.

    PubMed

    Balasubramanian, Sundar; Ortego, Jeffrey; Rusch, Kelly A; Boldor, Dorin

    2008-12-15

    A continuous microwave system to treat ballast water inoculated with Artemia salina cysts as a model invasive spore was tested for its efficacy in inactivating the cysts present. The system was tested at two different flow rates (1 and 2 L x min(-1)) and two different power levels (2.5 and 4.5 kW). Temperature profiles indicate that the system could deliver heating loads in excess of 100 degrees C in a uniform and near-instantaneous manner when using a heat recovery system. Except for a power and flow rate combination of 2.5 kW and 2 L x min(-1), complete inactivation of the cysts was observed at all combinations at holding times below 100 s. The microwave treatment was better or equal to the control treatment in inactivating the cysts. Use of heat exchangers increased the power conversion efficiency and the overall efficiency of the treatment system. Cost economics analysis indicates that in the present form of development microwave treatment costs are higher than the existing ballast water treatment methods. Overall, tests results indicated that microwave treatment of ballast water is a promising method that can be used in conjunction with other methods to form an efficient treatment system that can prevent introduction of potentially invasive spore forming species in non-native waters.

  18. Modeling of Heat and Moisture Transfer in Wood in Finish Drying by the Energy of a Microwave Field

    NASA Astrophysics Data System (ADS)

    Grinchik, N. N.; Adamovich, A. L.; Kizina, O. A.; Kharma, U. M.

    2015-01-01

    A physicomathematical model of heat and moisture transfer in drying materials in the region below the hygroscopicity limit, including also the heating by the energy of a microwave field, has been developed. The developed system of equations has been solved numerically for three cases of drying of a wooden plate: convective drying, drying by the microfield-field energy, and drying combining the above two methods, i.e., combined drying. Results of numerical calculations of the temperature, vapor-pressure, and moisture-content distributions in the cross section of the plate at different instants of time, and also of the change in the average moisture content and temperature in the process of drying, have been presented. The calculation results have been analyzed; conclusions on the differences and distinctive features of convective, microwave, and combined heating and drying have been drawn.

  19. Experimental Evaluation of the Heat Sink Effect in Hepatic Microwave Ablation

    PubMed Central

    Ringe, Kristina I.; Lutat, Carolin; Rieder, Christian; Schenk, Andrea; Wacker, Frank; Raatschen, Hans-Juergen

    2015-01-01

    Purpose To demonstrate and quantify the heat sink effect in hepatic microwave ablation (MWA) in a standardized ex vivo model, and to analyze the influence of vessel distance and blood flow on lesion volume and shape. Materials and Methods 108 ex vivo MWA procedures were performed in freshly harvested pig livers. Antennas were inserted parallel to non-perfused and perfused (700,1400 ml/min) glass tubes (diameter 5mm) at different distances (10, 15, 20mm). Ablation zones (radius, area) were analyzed and compared (Kruskal-Wallis Test, Dunn’s multiple comparison Test). Temperature changes adjacent to the tubes were measured throughout the ablation cycle. Results Maximum temperature decreased significantly with increasing flow and distance (p<0.05). Compared to non-perfused tubes, ablation zones were significantly deformed by perfused tubes within 15mm distance to the antenna (p<0.05). At a flow rate of 700ml/min ablation zone radius was reduced to 37.2% and 80.1% at 10 and 15mm tube distance, respectively; ablation zone area was reduced to 50.5% and 89.7%, respectively. Conclusion Significant changes of ablation zones were demonstrated in a pig liver model. Considerable heat sink effect was observed within a diameter of 15mm around simulated vessels, dependent on flow rate. This has to be taken into account when ablating liver lesions close to vessels. PMID:26222431

  20. Experimental Evaluation of the Heat Sink Effect in Hepatic Microwave Ablation.

    PubMed

    Ringe, Kristina I; Lutat, Carolin; Rieder, Christian; Schenk, Andrea; Wacker, Frank; Raatschen, Hans-Juergen

    2015-01-01

    To demonstrate and quantify the heat sink effect in hepatic microwave ablation (MWA) in a standardized ex vivo model, and to analyze the influence of vessel distance and blood flow on lesion volume and shape. 108 ex vivo MWA procedures were performed in freshly harvested pig livers. Antennas were inserted parallel to non-perfused and perfused (700,1400 ml/min) glass tubes (diameter 5mm) at different distances (10, 15, 20mm). Ablation zones (radius, area) were analyzed and compared (Kruskal-Wallis Test, Dunn's multiple comparison Test). Temperature changes adjacent to the tubes were measured throughout the ablation cycle. Maximum temperature decreased significantly with increasing flow and distance (p<0.05). Compared to non-perfused tubes, ablation zones were significantly deformed by perfused tubes within 15 mm distance to the antenna (p<0.05). At a flow rate of 700 ml/min ablation zone radius was reduced to 37.2% and 80.1% at 10 and 15 mm tube distance, respectively; ablation zone area was reduced to 50.5% and 89.7%, respectively. Significant changes of ablation zones were demonstrated in a pig liver model. Considerable heat sink effect was observed within a diameter of 15 mm around simulated vessels, dependent on flow rate. This has to be taken into account when ablating liver lesions close to vessels.

  1. Preparation of modified semi-coke by microwave heating and adsorption kinetics of methylene blue.

    PubMed

    Wang, Xin; Peng, Jin-Hui; Duan, Xin-Hui; Srinivasakannan, Chandrasekar

    2013-01-01

    Preparation of modified semi-coke has been achieved, using phosphoric acid as the modifying agent, by microwave heating from virgin semi-coke. Process optimization using a Central Composite Design (CCD) design of Response Surface Methodology (RSM) technique for the preparation of modifies semi-coke is presented in this paper. The optimum conditions for producing modified semi-coke were: concentration of phosphoric acid 2.04, heating time 20 minutes and temperature 587 degrees C, with the optimum iodine of 862 mg/g and yield of 47.48%. The textural characteristics of modified semi-coke were analyzed using scanning electron microscopy (SEM) and nitrogen adsorption isotherm. The BET surface area of modified semi-coke was estimated to be 989.60 m2/g, with the pore volume of 0.74 cm3/g and a pore diameter of 3.009 nm, with micro-pore volume contributing to 62.44%. The Methylene Blue monolayer adsorption capacity was found to be mg/g at K. The adsorption capacity of the modified semi-coke highlights its suitability for liquid phase adsorption application with a potential usage in waste water treatment.

  2. Study on formation of acrylamide in asparagine-sugar microwave heating systems using UPLC-MS/MS analytical method.

    PubMed

    Zhang, Yu; Fang, Haoran; Zhang, Ying

    2008-05-15

    Microwave heating can be regarded as a possible way to produce a considerable amount of acrylamide. The present study investigated the formation of acrylamide in asparagine-glucose, asparagine-fructose and asparagine-sucrose microwave heating systems by the response surface methodology (RSM) and the orthogonal array methodology (OAM). The acrylamide content was rapidly quantified by a validated ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method. Results of RSM study indicated that in the asparagine-glucose system, the acrylamide content increased in the combined condition of high temperature accompanying with short heating time (>190°C, <20min) or low temperature accompanying with long heating time (<180°C, >30min). In the asparagine-fructose system, the similar conclusion was made in the combined condition of high temperature accompanying with short heating time (>175°C, <20min) or low temperature accompanying with long heating time (<170°C, >25min). In the asparagine-sucrose system, the amount of acrylamide enhanced with the increase of both heating temperature and heating time. The fitted mathematic models were successfully applied to the quantification of acrylamide formation when the heating temperature and heating time fell into the ranges of 120-240°C and 5-35min simultaneously. OAM study showed that acrylamide is readily formed via heating binary precursors 5min at 180°C in the asparagine-glucose and asparagine-fructose systems. However, acrylamide is readily generated when the binary precursors are heated 15min at 180°C in the asparagine-sucrose system. Copyright © 2007 Elsevier Ltd. All rights reserved.

  3. Fast synthesis of nanocrystalline Mg2Si by microwave heating: a new route to nano-structured thermoelectric materials.

    PubMed

    Savary, Etienne; Gascoin, Franck; Marinel, Sylvain

    2010-12-07

    The ultra fast synthesis of nanocrystalline Mg(2)Si was carried out using microwave radiation. The elemental precursors were first milled together under dry conditions to get fine particles. The resulting mixture of powders of Mg and Si was cold pressed before being heated by microwave irradiation. Precursors and products were analyzed by X-ray diffraction and scanning electron microscopy. The high energy ball milling parameters utilized to prepare the reactive powders have quite an influence on the behavior of the mixture under irradiation. Moreover, SEM imaging demonstrates that the power and time of irradiation are crucial for the grain growth of the Mg(2)Si and must be adequately controlled in order to avoid the decomposition of the phase. Our results show that we successfully managed to easily and quickly synthesize homogeneous nanocrystalline Mg(2)Si with particle size smaller than 100 nm using a microwave power of only 175 W for two minutes on powders ball milled for two hours.

  4. Effect of growth durations on the formation of ZnO nanorods prepared using continuous microwave heating technique

    NASA Astrophysics Data System (ADS)

    Jumali, Mohammad Hafizuddin Hj; Lee, Hock Beng; Abbas, Haidr Abdulzahra

    2017-05-01

    The effect of growth durations on the formation of ZnO nanorods thin film under continuous microwave irradiation was investigated. ZnO nanorods were synthesized using a microwave-assisted seed mediated growth method. ZnO nanoseed layer was prepared on Si substrate using a sol-gel technique. The microwave-assisted seed mediated growth of ZnO nanorods was conducted at different growth durations, namely 15, 20 and 30 min by fixing the irradiation power at 110 W. XRD diffractogram shows that the hexagonal wurtzite crystal structure for all the samples exhibited a preferred growth orientation along the c-axis. FESEM micrographs reveal with increasing heating duration, the average diameter of ZnO nanorods increased considerably and contrarily, the surface density of nanorods reduced. PL analysis suggests that an extended growth duration has resulted in the creation of defects in nanorods films owing to the insufficient supply of precursor ions during growth process.

  5. Dual-mode antenna design for microwave heating and noninvasive thermometry of superficial tissue disease.

    PubMed

    Jacobsen, S; Stauffer, P R; Neuman, D G

    2000-11-01

    Hyperthermia therapy of superficial skin disease has proven clinically useful, but current heating equipment is somewhat clumsy and technically inadequate for many patients. The present effort describes a dual-purpose, conformal microwave applicator that is fabricated from thin, flexible, multilayer printed circuit board (PCB) material to facilitate heating of surface areas overlaying contoured anatomy. Preliminary studies document the feasibility of combining Archimedean spiral microstrip antennas, located concentrically within the central region of square dual concentric conductor (DCC) annular slot antennas. The motivation is to achieve homogeneous tissue heating simultaneously with noninvasive thermometry by radiometric sensing of blackbody radiation from the target tissue under the applicator. Results demonstrate that the two antennas have complimentary regions of influence. The DCC ring antenna structure produces a peripherally enhanced power deposition pattern with peaks in the outer corners of the aperture and a broad minimum around 50% of maximum centrally. In contrast, the Archimedean spiral radiates (or receives) energy predominantly along the boresight axis of the spiral, thus confining the region of influence to tissue located within the central broad minimum of the DCC pattern. Analysis of the temperature-dependent radiometer signal (brightness temperature) showed linear correlation of radiometer output with test load temperature using either the spiral or DCC structure as the receive antenna. The radiometric performance of the broadband Archimedean antenna was superior compared to the DCC, providing improved temperature resolution (0.1 degree C-0.2 degree C) and signal sensitivity (0.3 degree C-0.8 degree C/degree C) at all four 500 MHz integration bandwidths tested within the frequency range from 1.2 to 3.0 GHz.

  6. Survival of Listeria monocytogenes, E.coli 0157:H7 and Salmonella spp. on catfish fillets exposed to microwave heating in a continuous mode

    USDA-ARS?s Scientific Manuscript database

    Microwave (MW) heating using continuous power output with feedback control and a modified ingredient formulation, may provide better and consistent cooking of foods. Currently, household units with build-in inverter power supply units are available. These new generation microwave ovens provide con...

  7. Laboratory convection experiments with internal, noncontact, microwave generated heating, applied to Earth's mantle dynamics

    NASA Astrophysics Data System (ADS)

    Limare, Angela; Surducan, Emanoil; di Giuseppe, Erika; Surducan, Vasile; Neamtu, Camelia; Vilella, Kenny; Fourel, Loic; Farnetani, Cinzia; Kaminski, Edouard; Jaupart, Claude

    2014-05-01

    The thermal evolution of terrestrial planets is controlled by secular cooling and internal heating due to the decay of radiogenic isotopes, two processes which are equivalent from the standpoint of convection dynamics. Few studies have been devoted to the intrinsic characteristics of this form of convection, which are dominated by instabilities of a single boundary layer and which involve a non-isentropic interior thermal structure. Laboratory studies of such convection have been plagued by considerable technical difficulties and have been mostly restricted to aqueous solutions with moderate values of the Prandtl number, contrary to planetary mantles. Here, we describe a new laboratory setup to generate internal heating in controlled conditions based on microwave (MW) absorption. The advantages of our technique include, but are not limited to: (1) a volumetric heat source that can be localized or distributed in space, (2) selectively heating part of the volume with time varying intensity and space distribution. Our tank prototype had horizontal dimensions of 30 cm × 30 cm and 5 cm height. A uniform and constant temperature was maintained at the upper boundary by an aluminium heat exchanger and adiabatic conditions were imposed at the tank base. Experimental fluids were hydroxyethylcellulose - water mixtures whose viscosities were varied within a wide range depending on concentration. Experimental Prandtl numbers were set at values larger than 100. Thermochromic Liquid Crystals (TLC) were used to visualize the temperature field, and the velocity field was determined using Particle Image Velocimetry (PIV). The Rayleigh-Roberts number was varied from 105 to 107. We also conducted numerical simulations in 3D cartesian geometry using Stag-3D (Tackley 1993) to reproduce the experimental conditions, including the tank aspect ratio and the temperature dependence of physical properties. We observed that convection is driven by cold descending plumes generated at the upper

  8. Microwave radiation as heating method in the synthesis of titanium dioxide nanoparticles from hexafluorotitanate-organic salts

    SciTech Connect

    Estruga, Marc; Domingo, Concepcion; Ayllon, Jose A.

    2010-09-15

    Nanocrystalline anatase was obtained from ionic liquid-like precursors containing hexafluorotitanate-organic salts and less than 25 wt.% of water, and using boric acid as fluoride scavenger. Two alternative heating methods were explored using either a conventional oven or a domestic microwave apparatus. A significant reduction in the reaction time from 24 h to only few minutes was obtained using the microwave route. The as-prepared materials were characterized by X-ray diffraction, transmission electron microscopy, nitrogen sorption analysis, and attenuated total reflectance Fourier transformed infrared, X-ray photoelectronic and Raman spectroscopes. The convenience of using the microwave heating option was a function of the organic cation present in the precursor. Thus, organic ammonium cations containing only hydrocarbon substituents, such as diethylammonium, phenylammonium and benzyltrimethylammonium led to the precipitation of nanocrystalline anatase powder with high specific surface area (up to 120 m{sup 2} g{sup -1}) in a short processing time (1-3 min). Otherwise, alcohol and carboxylate functionalized cations decomposed under microwave treatment. Moreover, the choice of the organic cation allowed tuning several properties of the end material, such as particle size and pore morphology.

  9. Nanocomposite of LiFePO4 and mesoporous carbon prepared by microwave heating for rechargeable lithium batteries

    NASA Astrophysics Data System (ADS)

    Roh, Kwang Chul; Lee, Ho Jun; Lee, Jae-Won

    2013-11-01

    A nanocomposite of LiFePO4 and mesoporous carbon was synthesized from MgO-templated mesoporous carbon by microwave heating for use as a cathode material in rechargeable Li batteries. Our research group reported a composition method using a porous template in the a previous paper.[1] Despite its low carbon content, the present composite shows better electrochemical performance than our previously reported version. The LiFePO4 nanoparticles were homogeneously dispersed in the template because of the suppressed growth of LiFePO4 crystals in the template pores and small thermal gradient resulting from microwave heating. The three-dimensional conducting carbon network between the LiFePO4 nanoparticles led to excellent cycling stability and rate capability. No decrease in discharge capacity was observed up to 100 cycles, and 85% of the reversible capacity at a Crate of 0.1 was retained at a C-rate of 30.

  10. Formation and inhibition of Nε-(carboxymethyl)lysine in saccharide-lysine model systems during microwave heating.

    PubMed

    Li, Lin; Han, Lipeng; Fu, Quanyi; Li, Yuting; Liang, Zhili; Su, Jianyu; Li, Bing

    2012-10-31

    N(ε)-(carboxymethyl) lysine (CML) is the most abundant advanced glycation end product (AGE), and frequently selected as an AGEs marker in laboratory studies. In this paper, the formation and inhibition of N(ε)-(carboxymethyl)lysine in saccharide-lysine model systems during microwave heating have been studied. The microwave heating treatment significantly promoted the formation of CML during Maillard reactions, which was related to the reaction temperature, time and type of saccharide. The order of CML formation for different saccharides was lactose > glucose > sucrose. Then, the inhibition effect on CML by five inhibitors was further examined. According to the results, ascorbic acid and tocopherol did not affect inhibition of CML, in contrast, thiamin, rutin and quercetin inhibited CML formation, and the inhibitory effects were concentration dependent.

  11. Comparison of open microwave digestion and digestion by conventional heating for the determination of Cd, Cr, Cu and Pb in algae using transverse heated electrothermal atomic absorption spectrometry.

    PubMed

    Meeravali, N N; Kumar, S J

    2000-02-01

    A comparison between open microwave digestion and digestion by conventional heating was carried out for the determination of Cd, Cr, Cu, and Pb in two algae matrices using transverse heated electrothermal atomic absorption spectrometry (ETAAS). A SRM GBW 08504 cabbage was also analysed. These matrices were digested with HNO3, using a quartz vessel for microwave digestion and PFA vessel for digestion by conventional heating. Cd, Cu and Cr were determined without any modifier, while magnesium nitrate and ammonium phosphate mixed modifier was used for Pb. Results obtained by both the procedures were in good agreement with each other at 95% confidence level, and for SRM GBW 08504 cabbage the values agree well with the certified values. The limits of detection obtained were 0.0004, 0.060, 0.065 and 0.054 mg/kg for Cd, Cr, Cu, and Pb, respectively, using the microwave digestion process. The RSD for Cd was 10-15% and for the other elements 5-10%.

  12. Microwave heating synthesis and formation mechanism of chalcopyrite structured CuInS{sub 2} nanorods in deep eutectic solvent

    SciTech Connect

    Zhang, Jianjun Chen, Jun; Li, Qiang

    2015-03-15

    Graphical abstract: Chalcopyrite structured CuInS{sub 2} nanorods were synthesized by an environmentally friendly microwave heating method in deep eutectic solvent. Results show that microwave heating time plays an important role in the formation of CuInS{sub 2} nanostructure phase. The SEM results indicated that the obtained CuInS{sub 2} nanostructures display rod-like morphology with diameters of about 40 nm and lengths of about 400 nm. The UV–vis spectrum results indicated that the CuInS{sub 2} nanorods exhibit strong absorption from the entire visible light region to the near-infrared region beyond 1100 nm. The possible growth mechanism of CuInS{sub 2} nanorods was discussed. - Abstract: Chalcopyrite structured CuInS{sub 2} nanorods were synthesized by an environmentally friendly microwave heating method in deep eutectic solvent. The as-synthesized CuInS{sub 2} nanorods were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively. The results indicated that the obtained CuInS{sub 2} nanostructures display rod-like morphology with diameters of about 40 nm and lengths of about 400 nm. The influences of microwave heating time on the formation of CuInS{sub 2} phase were discussed. Ultraviolet–visible (UV–vis) and photoluminescence (PL) spectra were utilized to investigate the optical properties of CuInS{sub 2} nanorods. The results showed that the as-synthesized CuInS{sub 2} nanorods exhibit strong absorption from the entire visible light region to the near-infrared region beyond 1100 nm. PL spectrum of the as-synthesized CuInS{sub 2} nanorods displays an emission peak centered at 580 nm under excitation wavelength of 366 nm at room temperature. The possible growth mechanism of CuInS{sub 2} nanorods was discussed.

  13. Effects of extrusion, boiling, autoclaving, and microwave heating on lupine allergenicity.

    PubMed

    Alvarez-Alvarez, Javier; Guillamón, Eva; Crespo, Jesús F; Cuadrado, Carmen; Burbano, Carmen; Rodríguez, Julia; Fernández, Consuelo; Muzquiz, Mercedes

    2005-02-23

    Lupine flour has been reported as a causative agent of allergic reactions. However, the allergenicity of lupine after thermal processing is not well-known. For this purpose, the allergenic characteristics of lupine seeds after boiling (up to 60 min), autoclaving (121 degrees C, 1.18 atm, up to 20 min and 138 degrees C, 2.56 atm, up to 30 min), microwave heating (30 min), and extrusion cooking were studied. The IgE-binding capacity was analyzed by IgE-immunoblotting and CAP inhibition using a serum pool from 23 patients with lupine-specific IgE. Skin testing was carried out in four patients. An important reduction in allergenicity after autoclaving at 138 degrees C for 20 min was observed. IgE antibodies from two individual sera recognized bands at 23 and 29 kDa in autoclaved samples at 138 degrees C for 20 min. Autoclaving for 30 min abolished the IgE binding to these two components. A previously undetected band at 70 kDa was recognized by an individual serum. Therefore, prolonged autoclaving might have an important effect on the allergenicity of lupine with the majority of patients lacking IgE reactivity to these processed samples.

  14. Preparation of Reduced Iron Powders from Mill Scale with Microwave Heating: Optimization Using Response Surface Methodology

    NASA Astrophysics Data System (ADS)

    Ye, Qianxu; Zhu, Hongbo; Peng, Jinhui; Srinivasa Kannan, C.; Chen, Jian; Dai, Linqing; Liu, Peng

    2013-12-01

    Preparation of the reduced iron powder has been attempted with mill scale as the iron-bearing material and with wood charcoal as the reducing agent through microwave heating. The response surface methodology (RSM) is used to optimize the process conditions, with wood charcoal, process temperature, and holding time being the three process parameters. The regressed model equation eliminating the insignificant parameters through an analysis of variance (ANOVA) was used to optimize the process conditions. The optimum process parameters for the preparation of reduced iron powders have been identified to be the wood charcoal of 13.8 pct, a process temperature of 1391 K (1118 °C), and a holding time of 43 minutes. The optimum conditions resulted in reduced iron powders with a total iron content of 98.60 pct and a metallization ratio of 98.71 pct. X-ray fluorescence (XRF) was used to estimate the elemental contents of the reduced iron powder, which meets the specification of the HY100.23 first-class iron powder standard. Additionally X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) analysis were performed and the results are compiled.

  15. Stability and structural changes of horseradish peroxidase: microwave versus conventional heating treatment.

    PubMed

    Lopes, Lucas C; Barreto, Maria T M; Gonçalves, Karen M; Alvarez, Heiddy M; Heredia, Montserrat Fortuny; de Souza, Rodrigo Octavio M A; Cordeiro, Yraima; Dariva, Cláudio; Fricks, Alini T

    2015-02-01

    Effects of conventional heating (CH) and microwave (MW) on the structure and activity of horseradish peroxidase (HRP) in buffer solution were studied. CH incubation between 30 and 45 °C increased activity of HRP, reaching 170% of residual activity (RA) after 4-6 h at 45 °C. CH treatment at 50 and 60 °C caused HRP inactivation: RA was 5.7 and 16.7% after 12 h, respectively. Secondary and tertiary HRP structural changes were analyzed by circular dichroism (CD) and intrinsic fluorescence emission, respectively. Under CH, activation of the enzyme was attributed to conformational changes in secondary and tertiary structures. MW treatment had significant effects on the residual activity of HRP. MW treatment at 45 °C/30W followed by CH treatment 45 °C regenerated the enzyme activity. The greatest loss in activity occurred at 60 °C/60 W/30 min (RA 16.9%); without recovery of the original activity. The inactivation of MW-treated HRP was related to the loss of tertiary structure, indicating changes around the tryptophan environment.

  16. Feasibility study of microwave electron heating on the C-2 field-reversed configuration device

    SciTech Connect

    Yang, Xiaokang Ceccherini, Francesco; Dettrick, Sean; Binderbauer, Michl; Koehn, Alf; Petrov, Yuri

    2015-12-10

    Different microwave heating scenarios for the C-2 plasmas have been investigated recently with use of both the Genray ray-racing code and the IPF-FDMC full-wave code, and the study was focused on the excitation of the electron Bernstein wave (EBW) with O-mode launch. For a given antenna position on C-2 and the fixed 2D plasma density and equilibrium field profiles, simulations have been done for six selected frequencies (2.45 GHz, 5 GHz, 8 GHz, 18 GHz, 28 GHz, and 50 GHz). Launch angles have been optimized for each case in order to achieve high coupling efficiencies to the EBW by the O-X-B mode conversion process and high power deposition. Results show that among those six frequencies, the case of 8 GHz is the most promising scenario, which has both high mode conversion efficiency (90%) and the relatively deeper power deposition.

  17. Joule-heating-supported plasma filamentation and branching during subcritical microwave irradiation

    NASA Astrophysics Data System (ADS)

    Takahashi, Masayuki; Kageyama, Yoshiaki; Ohnishi, Naofumi

    2017-05-01

    Breakdown physics induced by a subcritical microwave was numerically reproduced by using a two-dimensional effective diffusion model for plasma transport and combining it with Maxwell's equations and a neutral gas dynamics equation. A discrete plasma structure was obtained when E0,rms/Ec ≧0.69 , where E0,rms is the root-mean-square of the incident electric field and Ec is the breakdown threshold, because an overcritical field that exceeded the breakdown threshold was formed in a region away from the bulk plasma by the wave reflection when the plasma reflectivity was increased by joule heating. However, a continuous plasma structure with a branching pattern was formed when E0,rms/Ec <0.69 because the enhanced electric-field region away from the bulk plasma never exceeded the breakdown threshold even when the plasma reflectivity increased. The propagation speed of the plasma front drastically decreased when E0,rms/Ec <0.69 because the plasma propagation was sustained by strong gas expansion, which required more time than wave-reflection and ionization processes.

  18. Synthesis and optical properties of MgO-doped ZnO microtubes using microwave heating

    NASA Astrophysics Data System (ADS)

    Al-Naser, Qusay A. H.; Zhou, Jian; Wang, Han; Liu, Guizhen; Wang, Lin

    2015-08-01

    The Zn1-xMgxO (x = 0%, 2% and 5%) microtubes have been successfully synthesized via a microwave heating method. The as synthesized microtubes were carefully investigated. Field emission scanning electron microscope (FE-SEM) showed that all the microtubes exhibit an exact hexagonal hollow structure with smooth surfaces and straight characteristics throughout their whole lengths. UV-Vis measurement indicates that the absorption peak for ZnO microtube was shifted from 378.88 nm (3.27 eV) to 369.91 nm (3.35 eV) for Zn0.95Mg0.05O microtube. Room temperature photoluminescence (PL) spectra showed that the intensity of UV emission peak decreased with increase of MgO concentration and the visible emission band showed a blue shift from 538.06812 nm for ZnO microtube to 529.54114 nm for Zn0.95Mg0.05O microtube. Energy-dispersive spectrometer (EDS) analysis revealed the presence of Zn and O as the only elementary components with the absence of MgO as a doping material.

  19. The Microwave Applications Theory Program at NRL and Some Chemistry Code Applications to Ionospheric Heating by Microwave Radiation.

    DTIC Science & Technology

    1980-08-26

    RADIATION 1. INTRODUCTION The advent of high power pulsed microwave devices, the magnetrons, at NRL,I which currently generate ’U 1 G Watt at X 1 0 cm and a...separation needed to sustain such a plasma. ( g ) relaxation of the disturbed air and the impact of the late time air chemistry on multi pulse breakdown...and the first negative bands of N 2+ . These two band systems correspond2 7 to N2 +(B2E - X2 E) and N2 (C 3Tu - B 3 g ) transitions, respectively. The

  20. Influence of spike lavender (Lavandula latifolia Med.) essential oil in the quality, stability and composition of soybean oil during microwave heating.

    PubMed

    Rodrigues, Nuno; Malheiro, Ricardo; Casal, Susana; Asensio-S-Manzanera, M Carmen; Bento, Albino; Pereira, José Alberto

    2012-08-01

    Lipids oxidation is one of the main factors leading to quality losses in foods. Its prevention or delay could be obtained by the addition of antioxidants. In this sense the present work intend to monitor the protective effects of Lavandula latifolia essential oil during soybean oil microwave heating. To achieve the proposed goal quality parameters (free acidity, peroxide value, specific coefficients of extinction and ΔK), fatty acids profile, tocopherols and tocotrienols composition, antioxidant activity and oxidative stability were evaluated in soybean oil with and without spike lavender essential oils (EO) submitted to different microwave heating exposure times (1, 3, 5, 10 and 15 min; 1000 Watt) with a standard domestic microwave equipment. Microwave heating induced severe quality and composition losses, mainly above 3 min of microwave heating, regardless the sample tested. However, spike lavender EO addition counteracts the oxidation comparatively to control oils, by presenting enhanced values in quality parameters. A higher protection in unsaturated fatty acids loss was also observed as well as a higher antioxidant activity and oxidative stability. The microwave heating effects were clearly different in the samples with essential oils addition, allowing discrimination from plain soybean oils by a principal component analysis, being also capable to discriminate the different heating times tested within each sample.

  1. Variations in the microwave radiation of the mesophere during heating of the ionosphere with high-power radiowaves

    NASA Astrophysics Data System (ADS)

    Kulikov, Yu. Yu.; Grigor'ev, G. I.; Krasil'nikov, A. A.; Frolov, V. L.

    2012-06-01

    We present the results of microwave observations of ozone radiation in the middle atmosphere during modification of the ionosphere by high-power short radio waves on March 27-28, 2011. The modification was performed on the "Sura" heating facility of the Radiophysical Research Institute (Nizhny Novgorod, Russia) by using two ozone meters oriented towards different regions in the sky. The effect of a decrease in the radiation intensity in the ozone line when the ionosphere is heated with high-power short-wave radio emission, which was discovered earlier, has been confirmed, and new data related to its characteristic have been obtained. A possible interpretation of this phenomenon is discussed.

  2. The use of self heating'' ceramics as crucibles for microwave melting metals and nuclear waste glass

    SciTech Connect

    Sturcken, E.F.

    1990-01-01

    Silicon carbide (SiC) crucibles were used to melt aluminum and copper in conventional and tuned microwave cavities at a microwave frequency of 2450 MHz. SiC crucibles were also used to vitrify and homogenize mixtures of nuclear waste and glass frit.

  3. The use of ``self heating`` ceramics as crucibles for microwave melting metals and nuclear waste glass

    SciTech Connect

    Sturcken, E.F.

    1990-12-31

    Silicon carbide (SiC) crucibles were used to melt aluminum and copper in conventional and tuned microwave cavities at a microwave frequency of 2450 MHz. SiC crucibles were also used to vitrify and homogenize mixtures of nuclear waste and glass frit.

  4. Toward Carbon-Nanotube-Based Theranostic Agents for Microwave Detection and Treatment of Breast Cancer: Enhanced Dielectric and Heating Response of Tissue-Mimicking Materials

    PubMed Central

    Mashal, Alireza; Sitharaman, Balaji; Li, Xu; Avti, Pramod; Sahakian, Alan V.; Booske, John H.; Hagness, Susan C.

    2010-01-01

    The experimental results reported in this letter suggest that single-walled carbon nanotubes (SWCNTs) have the potential to enhance dielectric contrast between malignant and normal tissue for microwave detection of breast cancer and facilitate selective heating of malignant tissue for microwave hyperthermia treatment of breast cancer. In this study, we constructed tissue-mimicking materials with varying concentrations of SWCNTs and characterized their dielectric properties and heating response. At SWCNT concentrations of less than 0.5% by weight, we observed significant increases in the relative permittivity and effective conductivity. In microwave heating experiments, we observed significantly greater temperature increases in mixtures containing SWCNTs. These temperature increases scaled linearly with the effective conductivity of the mixtures. This work is a first step towards the development of functionalized, tumor-targeting SWCNTs as theranostic (integrated therapeutic and diagnostic) agents for microwave breast cancer detection and treatment. PMID:20176534

  5. Toward carbon-nanotube-based theranostic agents for microwave detection and treatment of breast cancer: enhanced dielectric and heating response of tissue-mimicking materials.

    PubMed

    Mashal, Alireza; Sitharaman, Balaji; Li, Xu; Avti, Pramod K; Sahakian, Alan V; Booske, John H; Hagness, Susan C

    2010-08-01

    The experimental results reported in this paper suggest that single-walled carbon nanotubes (SWCNTs) have the potential to enhance dielectric contrast between malignant and normal tissue for microwave detection of breast cancer and facilitate selective heating of malignant tissue for microwave hyperthermia treatment of breast cancer. In this study, we constructed tissue-mimicking materials with varying concentrations of SWCNTs and characterized their dielectric properties and heating response. At SWCNT concentrations of less than 0.5% by weight, we observed significant increases in the relative permittivity and effective conductivity. In microwave heating experiments, we observed significantly greater temperature increases in mixtures containing SWCNTs. These temperature increases scaled linearly with the effective conductivity of the mixtures. This work is a first step towards the development of functionalized, tumor-targeting SWCNTs as theranostic (integrated therapeutic and diagnostic) agents for microwave breast cancer detection and treatment.

  6. New instrumentation for the comprehension of chemical reactions under microwave and classical heating with the aid of a wide frequency band dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Chevalier, S.; Meyer, O.; Weil, R.; Fourrierlamer, A.; Petit, A.; Loupy, A.; Maurel, F.

    2001-09-01

    An instrumentation system for measuring wide frequency band complex permittivity of a sample submitted to a microwave irradiation has been optimized in order to allow macroscopic temperature measurements. The reaction of saponification of aromatic esters is studied using this instrumentation. We take interest in the behavior of the ionic conductivity phenomenon occurring in the reactive medium during microwave heating, and we compare it with the results obtained under classical heating. We show that the activation energy associated with ionic conductivity is lower when the reaction is performed under microwaves than when it is performed under classical heating. We thus deduce that microwaves act on the reaction advancement as a catalyst, and thus makes the reaction easier.

  7. Crystallization evolution, microstructure and properties of sewage sludge-based glass-ceramics prepared by microwave heating.

    PubMed

    Tian, Yu; Zuo, Wei; Chen, Dongdong

    2011-11-30

    A Microwave Melting Reactor (MMR) was designed in this study which improved the microwave adsorption of sewage sludge to prepare glass-ceramics. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were used for the study of crystallization behavior and microstructure of the developed glass-ceramics. DSC and XRD analysis revealed that crystallization of the nucleated specimen in the region of 900-1000°C resulted in the formation of two crystalline phases: anorthite and wollastonite. When the crystallization temperature increased from 900 to 1000°C, the tetragonal wollastonite grains were subjected to tensile microstresses, causing the cracking of crystal. Al ions substituted partially Si ions and occupied tetrahedral sites, giving rise to the formation of anorthite. The relationship between microwave irradiation and crystal growth was studied and the result indicated that the microwave selective heating suppressed the crystal growth, giving apparent improvements in the properties of the glass-ceramics. The glass-ceramics products exhibited bending strength of 86.5-93.4 MPa, Vickers microhardness of 6.12-6.54 GPa and thermal expansion coefficient of 5.29-5.75 × 10(-6)/°C. The best chemical durability in acid and alkali solutions was 1.32-1.61 and 0.41-0.58 mg/cm(2), respectively, showing excellent durability in alkali solution. Copyright © 2011 Elsevier B.V. All rights reserved.

  8. A Microwave Thermostatic Reactor for Processing Liquid Materials Based on a Heat-Exchanger.

    PubMed

    Zhou, Yongqiang; Zhang, Chun; Xie, Tian; Hong, Tao; Zhu, Huacheng; Yang, Yang; Liu, Changjun; Huang, Kama

    2017-10-08

    Microwaves have been widely used in the treatment of different materials. However, the existing adjustable power thermostatic reactors cannot be used to analyze materials characteristics under microwave effects. In this paper, a microwave thermostatic chemical reactor for processing liquid materials is proposed, by controlling the velocity of coolant based on PLC (programmable logic controller) in different liquid under different constant electric field intensity. A nonpolar coolant (Polydimethylsiloxane), which is completely microwave transparent, is employed to cool the liquid materials. Experiments are performed to measure the liquid temperature using optical fibers, the results show that the precision of temperature control is at the range of ±0.5 °C. Compared with the adjustable power thermostatic control system, the effect of electric field changes on material properties are avoided and it also can be used to detect the properties of liquid materials and special microwave effects.

  9. Effect of microwave dielectric heating on intraparticle diffusion in reversed-phase liquid chromatography

    SciTech Connect

    Galinada, Wilmer; Guiochon, Georges A

    2005-08-01

    The influence of microwave (MW) irradiation on the mass transfer kinetics in reversed-phase liquid chromatography (RPLC) was studied by placing a column in a microwave oven and measuring the incremental change in the temperature of the column effluent stream at various microwave energies and mobile phase compositions. The microwave energy dissipated in the column was set between 15 and 200 W and the mobile phase composition used varied from 100 to 70, 50, and 10% methanol in water at 1.2 mL/min. At all the mobile phase compositions considered, the effluent temperature increased with increasing microwave energy. At 70% methanol, the mobile phase flow rate was set at 1.2, 2.0, and 2.8 mL/min. At 1.2 mL/min, the effluent temperatures at the lowest (15 W) and highest (200 W) microwave energy inputs were 25 {+-} 1 C and 41 {+-} 1 C for pure methanol, 25 {+-} 1 C and 48 {+-} 1 C for 70% methanol, 25 {+-} 1 C and 50 {+-} 1 C for 50% methanol, and, 25 {+-} 1 C and 52 {+-} 1 C for 10% methanol, respectively. With 70% methanol and microwave energy inputs of 15, 30, and 50 W, the effluent temperature did not change with increasing flow rate; a considerable change was observed at 100, 150, and 200 W between 1.2 and 2.0 mL/min and none between 2.0 and 2.8 mL/min. Chromatographic elution band profiles of propylbenzene were recorded under linear conditions, in 70% methanol solutions, for microwave energy inputs of 0, 15 and 30 W, at constant temperature. The intraparticle diffusion coefficient, D{sub e}, under microwave irradiation was ca. 20% higher than without irradiation. These preliminary results suggest that microwave irradiation may have a considerable influence on intraparticle diffusion in RPLC.

  10. High-power microwave transmission systems for electron-cyclotron-resonance plasma heating

    SciTech Connect

    Vernon, R.J.

    1991-08-01

    This progress report is for the sixth year of a grant from the US Department of Energy for the design, development, and fabrication of ECRH transmission and mode conversion systems to transport microwave power from a gyrotron to a magnetically confined plasma. The design and low-power testing of new and improved components for such systems and development of underlying theory is the focus of this project. Devising and improving component testing and diagnostic techniques is also an important part of this effort. The development of possible designs for sections of gyrotrons themselves, such as tapers or Vlasov-type launchers, in support of the Varian gyrotron development program is also considered when appropriate. We also provide support to other groups working on ECR heating of magnetically confined plasmas such as the groups at General Atomics, the University of Texas at Austin, and Lawrence Livermore National Laboratory. During the last year, we designed and had fabricated a two-dimensional Vlasov antenna system for a 110 GHz TE{sub 15,2} mode gyrotron for possible use at General Atomics. The system included the launcher section, a visor, main reflector, and focusing reflector. Programs to generate the tool-path profiles to cut the General Atomics'' Vlasov components on a milling machine were developed. We have also developed state-of-the art theory and programs for three-dimensional whispering-gallery-mode Vlasov antenna systems. A design for a 110 GHz TE{sub 01}-TE{sub 15,2} mode converter system for cold testing WGM Vlasov antenna systems was developed and is currently being fabricated also.

  11. New Perspectives on Longwave Imaging of Urban Heat Islands: Middle Infrared to Microwaves

    NASA Astrophysics Data System (ADS)

    Henebry, G. M.; Krehbiel, C. P.; Zheng, B.; Nguyen, L. H.; de Beurs, K.; Owsley, B.

    2015-12-01

    Urban populations are projected to increase throughout the century. As urban areas expand and increase in density as a result of population pressures, urban heat islands (UHIs) will grow and intensify. Characterization of UHIs using remote sensing has focused primarily on the use of thermal infrared (TIR) sensors. Remote sensing of TIR measures, at 1 km spatial resolution or coarser, land surface or skin temperatures to reveal the surface UHI (sUHI) in contrast to in situ approaches that measure air temperature at points in networks or along transects. The city, its suburbs, and rural matrix all emit longwave electromagnetic radiation at wavelengths both shorter and longer than TIR. Here we introduce the use of two other wavelength regions for UHI characterization. Our prior work has shown that the middle infrared (MIR) in the atmospheric window from 3-5 microns offers some advantages to imaging urban areas. We demonstrate a new method for characterizing the intensity and the seasonality of sUHI in the MIR for selected cities in North America and Europe using MODIS band 23. In contrast to MIR and TIR sensors, microwave radiometers (MWR) can retrieve both air temperature and water vapor, albeit at coarse spatial resolution (~25 km) relative to most urban areas. Using the AMSR-E/AMSR2 product time series, we show both the advantages and limitations of using MWR data to characterize UHIs in the megacities and major conurbations of North and South America. These new approaches to UHI characterization complement the traditional TIR methods to reveal other impacts of cities on their environment.

  12. Experimental observation of microwave absorption and electron heating due to the two plasmon decay instability and resonance absorption

    SciTech Connect

    Rasmussen, D.A.

    1981-01-01

    The interaction of intense microwaves with an inhomogeneous plasma is studied in two experimental devices. In the first device an investigation was made of microwave absorption and electron heating due to the parametric decay of microwaves into electron plasma waves (Two Plasmon Decay instability, TPDI), modeling a process which can occur near the quarter critical surface in laser driven pellets. P-polarized microwave (f = 1.2 GHz, P/sub 0/ less than or equal to 12 kW) are applied to an essentially collisionless, inhomogeneous plasma, in an oversized waveguide, in the U.C. Davis Prometheus III device. The initial density scale length near the quarter critical surface is quite long (L/lambda/sub De/ approx. = 3000 or k/sub 0/L approx. = 15). The observed threshold power for the TPDI is quite low (P/sub T/approx. = 0.1 kW or v/sub os//v/sub e/ approx. = 0.1). Near the threshold the decay waves only occur near the quarter critical surface. As the incident power is increased above threshold, the decay waves spread to lower densities, and for P/sub 0/ greater than or equal to lkW, (v/sub os//v/sub e/ greater than or equal to 0.3) suprathermal electron heating is strong for high powers (T/sub H/ less than or equal to 12 T/sub e/ for P/sub 0/ less than or equal to 8 kW or v/sub os//v/sub e/ less than or equal to 0.9).

  13. Microwave Pasteurization of Cooked Pasta: Effect of Process Parameters on Texture and Quality for Heat-and-Eat and Ready-to-Eat Meals.

    PubMed

    Joyner Melito, Helen S; Jones, Kari E; Rasco, Barbara A

    2016-06-01

    Pasta presents a challenge to microwave processing due to its unique cooking requirements. The objective of this study was to determine the effects of microwave processing on pasta physicochemical and mechanical properties. Fettuccine pasta was parboiled for selected times, then pasteurized using a Microwave Assisted Pasteurization System and stored under refrigeration for 1 wk. Samples were analyzed using microscopy, mechanical testing, and chemical analyses after storage. While no significant differences were observed for free amylose among fresh samples, samples parboiled for ≤6 min had significantly higher free amylose, suggesting reduced starch retrogradation. Increased heat treatment increased degree of protein polymerization, observed in microstructures as increased gluten strand thickness and network density. Firmness and extensibility increased with increased parboil time; however, extension data indicated an overall weakening of microwave-treated pasta regardless of total cooking time. Overall, microwave pasteurization was shown to be a viable cooking method for pasta.

  14. Performance of cellulose acetate - polyethersulphone blend membrane prepared using microwave heating for palm oil mill effluent treatment.

    PubMed

    Idris, A; Ahmed, I; Jye, H W

    2007-01-01

    The objective of this research is to investigate the performance of blend cellulose acetate (CA)-polyethersulphone (PES) membranes prepared using microwave heating (MWH) techniques and then compare it with blend CA-PES membranes prepared using conventional heating (CH) methods using bovine serum albumin solution. The superior membranes were then used in the treatment of palm oil mill effluent (POME). Various blends of CA-PES have been blended with PES in the range of 1-5 wt%. This distinctive series of dope formulations of blend CA/PES and pure CA was prepared using N, N-dimethylformamide (DMF) as solvent. The dope solution was prepared by MW heating for 5 min at a high pulse and the membranes were prepared by phase inversion method. The performances of these membranes were evaluated in terms of pure water and permeate flux, percentage removal of total suspended solids (TSS), chemical oxygen demand (COD) and biochemical oxygen demand (BOD). The results indicate that blend membranes prepared using the microwave technique is far more superior compared to that prepared using CH. Blend membranes with 19% CA, 1-3% PES and 80% of DMF solvent were found to be the best membrane formulation.

  15. A low cost technique for synthesis of gold nanoparticles using microwave heating and its application in signal amplification for detecting Escherichia Coli O157:H7 bacteria

    NASA Astrophysics Data System (ADS)

    Thanh Ngo, Vo Ke; Giang Nguyen, Dang; Phat Huynh, Trong; Lam, Quang Vinh

    2016-09-01

    In the present work a low cost technique for preparation of gold nanoparticles (AuNPs) using microwave heating was developed. The effect of different elements (precursor reagents, irradiation time, and microwave radiation power) on the final morphology of AuNPs obtained through the microwave assisted technique has been investigated. The characterization of the samples has been carried out by transmission electron microscopy, UV-vis absorption spectroscopy, Fourier transform infrared spectroscopy, and powder x-ray diffraction. The results showed that to some extent the above-mentioned characterizations influenced the size of synthetized nanoparticles and application of microwave heating has many advantages such as low cost, rapid preparation and highly uniform particles. As an application in quartz crystal microbalance (QCM) immunosensor, AuNPs are conjugated with the Escherichia coli (E.coli) O157:H7 antibodies for signal amplification to detect E.coli O157:H7 bacteria residual in QCM system.

  16. Investigation of temporal-spatial parameters of an urban heat island on the basis of passive microwave remote sensing

    NASA Astrophysics Data System (ADS)

    Khaikine, M. N.; Kuznetsova, I. N.; Kadygrov, E. N.; Miller, E. A.

    2006-02-01

    Quantitative measurements of the impact of an urban environment on the thermal state of the atmospheric boundary layer are presented. Temperature profiles up to the height of 600 m were obtained in a continuous series of measurements by three microwave profilers MTP-5 located in different areas of Moscow. The influence of this large city on urban heat island (UHI) parameters was estimated on occasions with stationary atmospheric processes and during cases with frontal passage. Two types of UHI were identified: one with a dome of urban warmth at all levels, and another with a low warm dome in combination with a lens of cold air above.

  17. Structural and Microwave Properties of Silica Xerogel Glass-Ceramic Sintered by Sub-millimeter Wave Heating using a Gyrotron

    NASA Astrophysics Data System (ADS)

    Aripin, H.; Mitsudo, S.; Prima, E. S.; Sudiana, I. N.; Tani, S.; Sako, K.; Fujii, Y.; Saito, T.; Idehara, T.; Sano, S.; Sunendar, B.; Sabchevski, S.

    2012-11-01

    In this paper, we present and discuss experimental results from a microwave sintering of silica glass-ceramics, produced from amorphous silica xerogel extracted from sago waste ash. As a radiation source for a microwave heating a sub-millimeter wave gyrotron (Gyrotron FU CW I) with an output frequency of 300 GHz has been used. The powders of the amorphous silica xerogel have been dry pressed and then sintered at temperatures ranging from 300 °C to 1200 °C. Microwave absorbing properties of the sintered samples were investigated by measuring the dielectric constant, the dielectric loss, and the reflection loss at different frequencies in the interval from 8.2 to 12.4 GHz. Furthermore, the characteristics of the formation process for producing silica glass-ceramics were studied using a Raman Spectroscopy and a Scanning Electron Microscopy (SEM). The results indicate that the samples sintered at 1200 °C are characterized by lower reflection losses and a better transparency due to the formation of a fully crystallized silica glass- ceramic at sufficiently high temperature.

  18. Application of Microwave Irradiation and Heat to Improve Gliadin Detection and Ricin ELISA Throughput with Food Samples.

    PubMed

    Garber, Eric A E; Thole, Joseph

    2015-06-11

    The utility of microwave irradiation to accelerate the onset of equilibrium and improve ELISA performance was examined using ELISAs for the detection of the plant toxin ricin and gliadin. The ricin ELISA normally requires several one hour incubations at 37 °C, a total assay time of approximately five hours, and employs a complex buffer containing PBS, Tween-20®, and non-fat milk. Different energy levels and pulse designs were compared to the use of abbreviated incubation times at 37 °C for the detection of ricin in food. The use of microwave irradiation had no significant advantage over the application of heat using an oven incubator and performed worse with some foods. In contrast, a gliadin ELISA that relied on 30 min incubation steps at room temperature and a salt-based buffer performed better upon irradiation but also displayed improvement upon incubating the microtiter plate at 37 °C. Whether microwave irradiation was advantageous compared to incubation in an oven was inconclusive. However, by abbreviating the incubation time of the ricin ELISA, it was possible to cut the assay time to less than 2 hours and still display LOD values < 10 ppb and recoveries of 78%-98%.

  19. Cashew Nut Quality as Influenced by Microwave Heating Used for Stored Grain Insect Control.

    PubMed

    Das, Ipsita; Shah, Narendra G; Kumar, Girish

    2014-01-01

    The objective of this work is to investigate the effect of microwave power levels (240, 360, and 480 W) and exposure time (30, 60, 90, 120, 180, and 240 s) on various properties of cashew nuts being used for disinfestation. The nuts were analyzed for moisture content, temperature rise, colour, free fatty acid (FFA) and peroxide value (PV). Experiments were conducted according to the response surface methodology. Increase in microwave power level and exposure time caused a decrease in moisture content, increase in temperature, and change in colour. Microwave treatment to target temperatures of 50-55°C (unfavorable for insect survival) made the PV of cashew nut decrease to 1.10 to 1.66 meq O2/Kg (from an initial value of 2.08 ± 0.05) and FFA value to 0.11 to 0.51% (from an initial value of 0.68 ± 0.03). Though PV and FFA values of microwave treated cashew nut were found to increase after 6 months of storage at room conditions, the values were within the limits for acceptable quality. Microwave treated cashew nuts were free from infestation and rancidity even after 6 months of storage while the untreated nuts were found to be heavily infested at the end of 1 month of storage.

  20. Cashew Nut Quality as Influenced by Microwave Heating Used for Stored Grain Insect Control

    PubMed Central

    Shah, Narendra G.; Kumar, Girish

    2014-01-01

    The objective of this work is to investigate the effect of microwave power levels (240, 360, and 480 W) and exposure time (30, 60, 90, 120, 180, and 240 s) on various properties of cashew nuts being used for disinfestation. The nuts were analyzed for moisture content, temperature rise, colour, free fatty acid (FFA) and peroxide value (PV). Experiments were conducted according to the response surface methodology. Increase in microwave power level and exposure time caused a decrease in moisture content, increase in temperature, and change in colour. Microwave treatment to target temperatures of 50–55°C (unfavorable for insect survival) made the PV of cashew nut decrease to 1.10 to 1.66 meq O2/Kg (from an initial value of 2.08 ± 0.05) and FFA value to 0.11 to 0.51% (from an initial value of 0.68 ± 0.03). Though PV and FFA values of microwave treated cashew nut were found to increase after 6 months of storage at room conditions, the values were within the limits for acceptable quality. Microwave treated cashew nuts were free from infestation and rancidity even after 6 months of storage while the untreated nuts were found to be heavily infested at the end of 1 month of storage. PMID:26904638

  1. Microstructural and mechanical investigation of aluminium alloy (Al 1050) melted by microwave hybrid heating

    NASA Astrophysics Data System (ADS)

    Shashank Lingappa, M.; Srinath, M. S.; Amarendra, H. J.

    2017-07-01

    Microwave processing of metals is an emerging area. Melting of bulk metallic materials through microwave irradiation is still immature. In view of this, the present paper discusses the melting of bulk Al 1050 metallic material through microwave irradiation. The melting process is carried out successfully in a domestic microwave oven with 900 W power at 2450 MHz frequency. Metallurgical and mechanical characterization of the processed and as-received material is carried out. Aluminium phase is found to be dominant in processed material when tested through x-ray diffraction (XRD). Microstructure study of as-cast metal through scanning electron microscopy (SEM) reveals the formation of uniform hexagonal grain structure free from pores and cavities. The average tensile strength of the cast material is found to be around 21% higher, when compared to as-received material. Vickers’ microhardness of the as-cast metal is measured and is 10% higher than that of the as-received metal. Radiography on as-cast metal shows no significant defects. Al 1050 material melted through microwave irradiation has exhibited superior properties than the as-received Al 1050.

  2. Microwave bonding of MEMS component

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B. (Inventor); Mai, John D. (Inventor); Jackson, Henry W. (Inventor); Budraa, Nasser K. (Inventor); Pike, William T. (Inventor)

    2005-01-01

    Bonding of MEMs materials is carried out using microwave. High microwave absorbing films are placed within a microwave cavity, and excited to cause selective heating in the skin of the material. This causes heating in one place more than another. Thereby minimizing the effects of the bonding microwave energy.

  3. Preparation of activated carbon by microwave heating of langsat (Lansium domesticum) empty fruit bunch waste.

    PubMed

    Foo, K Y; Hameed, B H

    2012-07-01

    The feasibility of langsat empty fruit bunch waste for preparation of activated carbon (EFBLAC) by microwave-induced activation was explored. Activation with NaOH at the IR ratio of 1.25, microwave power of 600 W for 6 min produced EFBLAC with a carbon yield of 81.31% and adsorption uptake for MB of 302.48 mg/g. Pore structural analysis, scanning electron microscopy and Fourier transform infrared spectroscopy demonstrated the physical and chemical characteristics of EFBLAC. Equilibrium data were best described by the Langmuir isotherm, with a monolayer adsorption capacity of 402.06 mg/g, and the adsorption kinetics was well fitted to the pseudo-second-order equation. The findings revealed the potential to prepare high quality activated carbon from langsat empty fruit bunch waste by microwave irradiation. Copyright © 2012 Elsevier Ltd. All rights reserved.

  4. Temperature dependence and shape effect in high-temperature microwave heating of nickel oxide powders

    NASA Astrophysics Data System (ADS)

    Sugawara, H.; Kashimura, K.; Hayashi, M.; Matsumuro, T.; Watanabe, T.; Mitani, T.; Shinohara, N.

    2015-02-01

    The temperature dependence of microwave absorption was investigated for Ni1-yO particles over the frequency range 2.0-13.5 GHz and temperature range 25-1000 °C. Using a coaxial transmission line method with a network analyzer, both the real and imaginary parts of the relative permittivity (ε‧r and ε″r, respectively) and permeability (μ‧r and μ″r, respectively) were measured; finding that both are largely dependent on the temperature at all frequencies. Furthermore, permeability loss factors related to shape effects were observed at high frequencies, indicating an increase in the microwave-absorption properties. A modified form of Mie's theory was applied to discuss these effects, wherein a spherical model demonstrating a close fit to the shape effect data suggests a more complex microwave-absorption behavior at increased temperature.

  5. Effect of heat treatment on microwave absorption properties of Ni-Zn-Mg-La ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Wei, Shicheng; Xu, Binshi; Wang, Yujiang; Tian, Haoliang; Tong, Hui

    2014-01-01

    Spinel structure Ni-Zn-Mg-La ferrites have been prepared by the sol-gel route and investigated as a radar absorbing material (RAM) in a frequency range of 1-18 GHz. The structure and morphological studies on the nanoparticles of the ferrites have been carried out using X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The complex permeability and complex permittivity are measured by a network analyzer. The electromagnetic wave loss and microwave absorbing property are studied as a function of frequency, annealing temperature and thickness of the absorber. The results indicate that electromagnetic wave loss of the ferrite only annealed at 850 °C shows two peaks. The reflection loss varies with the change of the annealing temperature. The absorber annealed at 850 °C exhibits the best microwave absorbing properties, which is suitable for microwave absorption materials.

  6. Microwave selective heating for size effect of water droplet in W/O emulsion with sorbitan fatty acid monostearate surfactant

    NASA Astrophysics Data System (ADS)

    Sumi, Takuya; Horikoshi, Satoshi

    2015-09-01

    A stable water/oil (W/O) emulsion was prepared by adjustment with sorbitan fatty acid monoester surfactants. The prepared W/O emulsion was stable for 60 min in the atmosphere; however, the formation of non-uniform water droplets in the height of the emulsion in the quartz tube reactor were observed by the backscattering measurements with an infrared laser at 850 nm. The increase of temperature under microwave irradiation was influenced sensitively by the position of those water droplets. Those results were caused from the size and concentration of water droplets in the W/O emulsion. On the other hand, selective heating of the water droplets caused heating of the entire W/O emulsion, although the temperature difference between the water droplets and the oil phase was 20 °C.

  7. Microwave-specific acceleration of a Friedel-Crafts reaction: evidence for selective heating in homogeneous solution.

    PubMed

    Rosana, Michael R; Hunt, Jacob; Ferrari, Anthony; Southworth, Taylor A; Tao, Yuchuan; Stiegman, Albert E; Dudley, Gregory B

    2014-08-15

    Thermally promoted Friedel-Crafts benzylation of arene solvents has been examined under both conventional convective heating with an oil bath and heating using microwave (MW) energy. Bulk solution temperatures-as measured by internal and external temperature probes and as defined by solvent reflux-were comparable in both sets of experiments. MW-specific rate enhancements were documented under certain conditions and not others. The observed rate enhancements at a given temperature are proposed to arise from selective MW heating of polar solutes, perturbing thermal equilibrium between the solute and bulk solution. Central to MW-specific thermal phenomena is the difference between heat and temperature. Temperature is a measure of the ensemble average kinetic molecular energy of all solution components, but temperature does not provide information about solute-specific energy differences that may arise as a consequence of selective MW heating. Enhanced chemical reactivity of the MW-absorbing solute can be described as a MW-specific "extra-temperature thermal effect", because the measurable solution temperature only captures a portion of the solute kinetic molecular energy. Experimental factors that favor MW-specific rate enhancements are discussed with an eye toward future development of MW-actuated organic reactions, in which the observed thermal reactivity exceeds what is predicted from temperature-based Arrhenius calculations.

  8. The Earth's mantle in a microwave oven: thermal convection driven by a heterogeneous distribution of heat sources

    NASA Astrophysics Data System (ADS)

    Fourel, Loïc; Limare, Angela; Jaupart, Claude; Surducan, Emanoil; Farnetani, Cinzia G.; Kaminski, Edouard C.; Neamtu, Camelia; Surducan, Vasile

    2017-08-01

    Convective motions in silicate planets are largely driven by internal heat sources and secular cooling. The exact amount and distribution of heat sources in the Earth are poorly constrained and the latter is likely to change with time due to mixing and to the deformation of boundaries that separate different reservoirs. To improve our understanding of planetary-scale convection in these conditions, we have designed a new laboratory setup allowing a large range of heat source distributions. We illustrate the potential of our new technique with a study of an initially stratified fluid involving two layers with different physical properties and internal heat production rates. A modified microwave oven is used to generate a uniform radiation propagating through the fluids. Experimental fluids are solutions of hydroxyethyl cellulose and salt in water, such that salt increases both the density and the volumetric heating rate. We determine temperature and composition fields in 3D with non-invasive techniques. Two fluorescent dyes are used to determine temperature. A Nd:YAG planar laser beam excites fluorescence, and an optical system, involving a beam splitter and a set of colour filters, captures the fluorescence intensity distribution on two separate spectral bands. The ratio between the two intensities provides an instantaneous determination of temperature with an uncertainty of 5% (typically 1K). We quantify mixing processes by precisely tracking the interfaces separating the two fluids. These novel techniques allow new insights on the generation, morphology and evolution of large-scale heterogeneities in the Earth's lower mantle.

  9. Rapid and sensitive detection of troponin I in human whole blood samples by using silver nanoparticle films and microwave heating.

    PubMed

    Aslan, Kadir; Grell, Tsehai A J

    2011-05-01

    Cardiovascular diseases are among the leading causes of mortality in developed countries. It is widely recognized that troponin I (TnI) can be used for the assessment of a myocardial infarction. We investigated the use of the microwave-accelerated and metal-enhanced fluorescence (MA-MEF), a technique based on the combined use of low-power microwave heating, silver nanoparticle films (SNFs), and fluorescence spectroscopy for the detection of TnI from human whole blood samples. SNFs were deposited onto amine-modified glass microscope slides by use of Tollen's reaction scheme and characterized by optical absorption spectroscopy and scanning electron microscopy. The detection of TnI from buffer solutions and human whole blood samples on SNFs was carried out by using fluorescence-based immunoassays at room temperature (control immunoassay, 2 h total assay time) or microwave heating (MA-MEF-based immunoassay, 1 min total assay time). We found that the lower limits of detection for TnI from buffer solutions in the control immunoassay and MA-MEF-based immunoassay were 0.1 μg/L and 0.005 μg/L, respectively. However, we were unable to detect TnI in whole blood samples in the control immunoassays owing to the coagulation of whole blood within 5 min of the incubation step. The use of the MA-MEF technique allowed detection of TnI from whole blood samples in 1 min with a lower detection limit of 0.05 μg/L. The MA-MEF-based immunoassay is one of the fastest reported quantitative detection methodos for detection of TnI in human whole blood and has low detection limits similar to those obtained with commercially available immunoassays.

  10. Correlation of Heating Rates, Crystal Structures, and Microwave Dielectric Properties of Li2ZnTi3O8 Ceramics

    NASA Astrophysics Data System (ADS)

    Lu, Xuepeng; Zheng, Yong; Huang, Qi; Xiong, Weihao

    2015-11-01

    The correlation of heating rates, crystal structures, and microwave dielectric properties of Li2ZnTi3O8 ceramics was thoroughly investigated. Ionic polarizability, atomic packing fractions, bond strengths, and octahedral distortion of Li2ZnTi3O8 ceramics were calculated on the basis of structure refinement data. The "black core" phenomenon resulting from reduction of Ti4+ ions was observed for Li2ZnTi3O8 ceramic sintered at 1°/min; reduction of Ti4+ ions could be limited by heating more rapidly. For heating rates from 1 to 7°/min, the dielectric constants ( ɛ r) of Li2ZnTi3O8 ceramics were mainly determined by ionic polarizability. The temperature coefficient of the resonant frequency ( τ f ) of Li2ZnTi3O8 ceramics was determined by bond strengths. Li2ZnTi3O8 ceramic sintered at 1°/min had the lowest quality factor ( Q × f); this was related to the high dielectric loss as a result of oxygen vacancies formed by reduction of Ti4+ ions. Q × f values of Li2ZnTi3O8 ceramics also decreased with increasing heating rate from 3 to 7°/min, owing to reduced packing fractions and average grain sizes. Li2ZnTi3O8 ceramic sintered at 3°/min had the optimum microwave dielectric properties of ɛ r = 26.6, Q × f = 83,563 GHz, and τ f = -12.4 ppm/°C.

  11. Temperature influence on product distribution and characteristics of derived residue and oil in wet sludge pyrolysis using microwave heating.

    PubMed

    Lin, Kuo-Hsiung; Lai, Nina; Zeng, Jun-Yan; Chiang, Hung-Lung

    2017-04-15

    Sludge taken from a wastewater treatment plant of the petrochemical industry was dewatered and pyrolyzed to produce liquid oil as an alternative fuel via microwave heating. Element contents of dried sludge were 45.9±3.85wt.% carbon, 7.70±1.43wt.% hydrogen, 4.30±0.77wt.% nitrogen and 3.89±0.52wt.% sulfur. Two major thermal degradation peaks of sludge were determined during the microwave pyrolysis process, one at 325-498K (most of the water was vaporized, and the weight loss was over 85wt.%) and the other at 548-898K for sludge constituent decomposition. Zn content was high in the dried raw material and residues. Other toxic elements such as Ni, Cr, Pb, As and Cd contents were 0.61-0.99, 0.18-0.46, 0.15-0.25, 0.018-0.034, and 0.006-0.017mg/g, respectively. About 14-20wt.% of oil was produced based on the dried sludge cake, and the oil major elements were C (69-72wt.%), H (5.7-6.7wt.%), N (1.9-2.2wt.%), and S (0.58-0.82wt.%). The heat values of liquid oils were 8700-9200kcal/kg at 400-800°C. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Effects of antigen retrieval by microwave heating in formalin-fixed tissue sections on a broad panel of antibodies.

    PubMed

    von Wasielewski, R; Werner, M; Nolte, M; Wilkens, L; Georgii, A

    1994-09-01

    Formaldehyde fixation of biopsy specimens for routine purposes has often been held responsible for the poor reproducibility of immunohistochemical studies. Recently, antigen retrieval (AGR) using microwave irradiation was described as a potential tool to enhance immunostaining. A comparison of conventional staining and staining after microwave heating was performed for 52 markers, using tissues fixed in formaldehyde for 24 h, 1 to 6 weeks and 3 years respectively, as well as consultant case material. After adequate duration of fixation (24 h), only a few markers (17%) showed better results after AGR, but this percentage was increased to 50% when tissues were fixed for longer periods. Maximal enhancement was obtained in the group of consultant cases (58% of tested markers demonstrated better staining results), in which the period of fixation and tissue processing was unknown. To achieve reliable enhancement with AGR, continuous heating (100 degrees C) should not be shorter than 20 min. In conclusion, AGR may become the most important tool to simplify and equalize immunohistochemical techniques, if critically evaluated.

  13. Microwave flow and conventional heating effects on the physicochemical properties, bioactive compounds and enzymatic activity of tomato puree.

    PubMed

    Arjmandi, Mitra; Otón, Mariano; Artés, Francisco; Artés-Hernández, Francisco; Gómez, Perla A; Aguayo, Encarna

    2017-02-01

    Thermal processing causes a number of undesirable changes in physicochemical and bioactive properties of tomato products. Microwave (MW) technology is an emergent thermal industrial process that offers a rapid and uniform heating, high energy efficiency and high overall quality of the final product. The main quality changes of tomato puree after pasteurization at 96 ± 2 °C for 35 s, provided by a semi-industrial continuous microwave oven (MWP) under different doses (low power/long time to high power/short time) or by conventional method (CP) were studied. All heat treatments reduced colour quality, total antioxidant capacity and vitamin C, with a greater reduction in CP than in MWP. On the other hand, use of an MWP, in particular high power/short time (1900 W/180 s, 2700 W/160 s and 3150 W/150 s) enhanced the viscosity and lycopene extraction and decreased the enzyme residual activity better than with CP samples. For tomato puree, polygalacturonase was the more thermo-resistant enzyme, and could be used as an indicator of pasteurization efficiency. MWP was an excellent pasteurization technique that provided tomato puree with improved nutritional quality, reducing process times compared to the standard pasteurization process. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  14. Sodium nitrate containing mixture for producing ceramic-glass-ceramic seal by microwave heating

    DOEpatents

    Blake, R.D.; Meek, T.T.

    1984-10-10

    A mixture for, and method of using such a mixture, for producing a ceramic-glass-ceramic seal by the use of microwave energy are disclosed, wherein the mixture comprises a glass sealing material, a coupling agent, and an oxidizer. The seal produced exhibits greater strength due to its different microstructure. Sodium nitrate is the most preferred oxidizer.

  15. Mathematical Modeling of Microwave-Assisted Convective Heating and Drying of Grapes

    USDA-ARS?s Scientific Manuscript database

    This research studied the processing performance and product quality of Thompson seedless grapes dried using microwave-assisted convective hot air drying as well as the effect of blanching and dipping pretreatments. Two pretreatment methods were compared, dipping into 2% ethyl oleate (V/V) and 5% p...

  16. Method for producing ceramic-glass-ceramic seals by microwave heating

    DOEpatents

    Blake, Rodger D.; Meek, Thomas T.

    1986-01-01

    Method for producing a ceramic-glass-ceramic seal by the use of microwave energy, and a sealing mixture which comprises a glass sealing material, a coupling agent, and an oxidizer. The seal produced exhibits greater strength due to its different microstructure. Sodium nitrate is the most preferred oxidizer.

  17. Comparison of heat and mass transfer of different microwave-assisted extraction methods of essential oil from Citrus limon (Lisbon variety) peel.

    PubMed

    Golmakani, Mohammad-Taghi; Moayyedi, Mahsa

    2015-11-01

    Dried and fresh peels of Citrus limon were subjected to microwave-assisted hydrodistillation (MAHD) and solvent-free microwave extraction (SFME), respectively. A comparison was made between MAHD and SFME with the conventional hydrodistillation (HD) method in terms of extraction kinetic, chemical composition, and antioxidant activity. Higher yield results from higher extraction rates by microwaves and could be due to a synergy of two transfer phenomena: mass and heat acting in the same way. Gas chromatography/mass spectrometry (GC/MS) analysis did not indicate any noticeable differences between the constituents of essential oils obtained by MAHD and SFME, in comparison with HD. Antioxidant analysis of the extracted essential oils indicated that microwave irradiation did not have adverse effects on the radical scavenging activity of the extracted essential oils. The results of this study suggest that MAHD and SFME can be termed as green technologies because of their less energy requirements per ml of essential oil extraction.

  18. Method and apparatus for selectively annealing heterostructures using microwave

    NASA Technical Reports Server (NTRS)

    Atwater, Harry A. (Inventor); Brain, Ruth A. (Inventor); Barmatz, Martin B. (Inventor)

    1998-01-01

    The present invention discloses a process for selectively annealing heterostructures using microwaves. A heterostructure, comprised of a material having higher microwave absorption and a material having lower microwave absorption, is exposed to microwaves in the cavity. The higher microwave absorbing material absorbs the microwaves and selectively heats while the lower microwave absorbing material absorbs small amounts of microwaves and minimally heats. The higher microwave absorbing material is thereby annealed onto the less absorbing material which is thermally isolated.

  19. Method and apparatus for selectively annealing heterostructures using microwaves

    NASA Technical Reports Server (NTRS)

    Atwater, Harry A. (Inventor); Brain, Ruth A. (Inventor); Barmatz, Martin B. (Inventor)

    1998-01-01

    The present invention discloses a process for selectively annealing heterostructures using microwaves. A heterostructure, comprised of a material having higher microwave absorption and a material having lower microwave absorption, is exposed to microwaves in the cavity. The higher microwave absorbing material absorbs the microwaves and selectively heats while the lower microwave absorbing material absorbs small amounts of microwaves and minimally heats. The higher microwave absorbing material is thereby annealed onto the less absorbing material which is thermally isolated.

  20. The heat-shock factor is not activated in mammalian cells exposed to cellular phone frequency microwaves.

    PubMed

    Laszlo, Andrei; Moros, Eduardo G; Davidson, Teri; Bradbury, Matt; Straube, William; Roti Roti, Joseph

    2005-08-01

    There has been considerable interest in the biological effects of exposure to radiofrequency electromagnetic radiation, given the explosive growth of cellular telephone use, with the possible induction of malignancy being a significant concern. Thus the determination of whether nonthermal effects of radiofrequency electromagnetic radiation contribute to the process leading to malignancy is an important task. One proposed pathway to malignancy involves the induction of the stress response by exposures to cell phone frequency microwaves. The first step in the induction of the stress response is the activation of the DNA-binding activity of the specific transcription factor involved in this response, the heat-shock factor (HSF). The DNA-binding activity of HSF in hamster, mouse and human cells was determined after acute and continuous exposures to frequency domain multiple access (FDMA)- or code domain multiple access (CDMA)-modulated microwaves at low (0.6 W/kg) or high (approximately 5 W/kg) SARs at frequencies used for mobile communication. The DNA-binding activity of HSF was monitored using a gel shift assay; the calibration of this assay indicated that an increase of approximately 10% in the activation of the DNA-binding activity of HSF after a 1 degrees C increase in temperature could be detected. We failed to detect any increase in the DNA-binding ability of HSF in cultured mammalian cells as a consequence of any exposure tested, within the sensitivity of our assay. Our results do not support the notion that the stress response is activated as a consequence of exposure to microwaves of frequencies associated with mobile communication devices.

  1. Behavior of microwave-heated silicon carbide particles at frequencies of 2.0–13.5 GHz

    SciTech Connect

    Sugawara, H.; Hayashi, M.; Ishihara, S.; Kashimura, K.; Mitani, T.; Shinohara, N.

    2014-07-21

    Silicon carbide is a key material in microwave (MW) processing and is used widely as a thermal insulator and catalytic agent. In this study, we experimentally investigated the temperature dependence of the MW-absorption properties of SiC particles at frequencies of 2.0–13.5 GHz. We heated SiC particles of different sizes using MW radiation. The heating behaviors of the particles were then compared with their MW-absorption properties. The heating behavior of the particles was dependent on their radii; this result was in keeping with theoretical predictions. Furthermore, the β-SiC particles exhibited anomalous behaviors when subjected to microwave heating at temperatures of 1100 °C and higher. These behaviors were attributable to the transformation of β-SiC into the α-phase. The underlying mechanism for this transformation is discussed on the basis of the results of X-ray diffraction analysis.

  2. Effect of microwave heating on the migration of dioctyladipate and acetyltributylcitrate plasticizers from food-grade PVC and PVDC/PVC films into olive oil and water.

    PubMed

    Badeka, A B; Kontominas, M G

    1996-04-01

    Migration of dioctyladipate (DOA) and acetyltributylcitrate (ATBC) plasticizers from plasticized polyvinylchloride (PVC) and polyvinylidene chloride (PVDC)/PVC (Saran) films into both olive oil and distilled water during microwave heating has been studied. The plasticizer migrating into olive oil and water was determined using an indirect GC method after saponification of the ester-type plasticizer (DOA or ATBC) and subsequent collection of the alcohol component of the ester, namely: 2-ethyl-1-hexanol and 1-butanol, respectively. Migration was dependent on heating time, microwave power setting, the nature of the food simulant and the initial concentration of the plasticizer in the film. Migration of DOA into olive oil reached equilibrium after heating for 10 min at full power (604.6 mg DOA/l). Migration into distilled water was 74.1 mg/l after 8 min of microwave cooking at full power. The amount of ATBC migrating into olive oil reached equilibrium after heating for 10 min at full power (73.9 mg ATBC/l). Migration into distilled water was 4.1 mg/l after heating at full power for 8 min. Control samples containing olive oil gave DOA migration values which were significantly higher than the upper limit for global migration (60 mg/l) set by the European Community. It is proposed that PVC should not be used in direct contact with food in the microwave oven, while Saran may be used with caution in microwave heating and reheating applications, avoiding its direct contact with high fat foodstuffs.

  3. Influence of water activity on inactivation of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes in peanut butter by microwave heating.

    PubMed

    Song, Won-Jae; Kang, Dong-Hyun

    2016-12-01

    This study evaluated the efficacy of a 915 MHz microwave with 3 different electric power levels to inactivate three pathogens in peanut butter with different aw. Peanut butter inoculated with Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium and Listeria monocytogenes (0.3, 0.4, and 0.5 aw) were treated with a 915 MHz microwave with 2, 4, and 6 kW for up to 5 min. Six kW 915 MHz microwave treatment for 5 min reduced these three pathogens by 1.97 to >5.17 log CFU/g. Four kW 915 MHz microwave processing for 5 min reduced these pathogens by 0.41-1.98 log CFU/g. Two kW microwave heating did not inactivate pathogens in peanut butter. Weibull and Log-Linear + Shoulder models were used to describe the survival curves of three pathogens because they exhibited shouldering behavior. Td and T5d values were calculated based on the Weibull and Log-Linear + Shoulder models. Td values of the three pathogens were similar to D-values of Salmonella subjected to conventional heating at 90 °C but T5d values were much shorter than those of conventional heating at 90 °C. Generally, increased aw resulted in shorter T5d values of pathogens, but not shorter Td values. The results of this study can be used to optimize microwave heating pasteurization system of peanut butter.

  4. Precipitation and Latent Heating Distributions from Satellite Passive Microwave Radiometry. Part 2; Evaluation of Estimates Using Independent Data

    NASA Technical Reports Server (NTRS)

    Yang, Song; Olson, William S.; Wang, Jian-Jian; Bell, Thomas L.; Smith, Eric A.; Kummerow, Christian D.

    2004-01-01

    Rainfall rate estimates from space-borne k&ents are generally accepted as reliable by a majority of the atmospheric science commu&y. One-of the Tropical Rainfall Measuring Mission (TRh4M) facility rain rate algorithms is based upon passive microwave observations fiom the TRMM Microwave Imager (TMI). Part I of this study describes improvements in the TMI algorithm that are required to introduce cloud latent heating and drying as additional algorithm products. Here, estimates of surface rain rate, convective proportion, and latent heating are evaluated using independent ground-based estimates and satellite products. Instantaneous, OP5resolution estimates of surface rain rate over ocean fiom the improved TMI algorithm are well correlated with independent radar estimates (r approx. 0.88 over the Tropics), but bias reduction is the most significant improvement over forerunning algorithms. The bias reduction is attributed to the greater breadth of cloud-resolving model simulations that support the improved algorithm, and the more consistent and specific convective/stratiform rain separation method utilized. The bias of monthly, 2.5 deg. -resolution estimates is similarly reduced, with comparable correlations to radar estimates. Although the amount of independent latent heating data are limited, TMI estimated latent heating profiles compare favorably with instantaneous estimates based upon dual-Doppler radar observations, and time series of surface rain rate and heating profiles are generally consistent with those derived from rawinsonde analyses. Still, some biases in profile shape are evident, and these may be resolved with: (a) additional contextual information brought to the estimation problem, and/or; (b) physically-consistent and representative databases supporting the algorithm. A model of the random error in instantaneous, 0.5 deg-resolution rain rate estimates appears to be consistent with the levels of error determined from TMI comparisons to collocated radar

  5. Batch and continuous flow preparation of Hantzsch 1,4-dihydropyridines under microwave heating and simultaneous real-time monitoring by Raman spectroscopy. An exploratory study.

    PubMed

    Christiaens, Sylvain; Vantyghem, Xavier; Radoiu, Marilena; Vanden Eynde, Jean Jacques

    2014-07-09

    Dialkyl 1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylates have been prepared in a batch mode under conventional heating as well as under continuous flow conditions in the Miniflow 200SS, Sairem's microwave-assisted batch and continuous flow equipment. Real-time monitoring of the reactions by Raman spectroscopy enabled to compare both heating modes and to determine (optimized) reaction times.

  6. Removal of Pb(II) from water by the activated carbon modified by nitric acid under microwave heating.

    PubMed

    Yao, Shuheng; Zhang, Jiajun; Shen, Dekui; Xiao, Rui; Gu, Sai; Zhao, Ming; Liang, Junyu

    2016-02-01

    The rice husk based activated carbon (RH-AC) was treated by nitric acid under microwave heating, in order to improve its capability for the removal of heavy metal ions from water. The optimal conditions for the modification of RH-AC (M-RH-AC) were determined by means of orthogonal array experimental design, giving those as the concentration of nitric acid of 8mol/L, modification time of 15min, modification temperature of 130°C and microwave power of 800W. The characteristics of the M-RH-AC and RH-AC were examined by BET, XRD, Raman spectrum, pH titration, zeta potential, Boehm titration and FTIR analysis. The M-RH-AC has lower pore surface area, smaller crystallite, lower pHIEP and more oxygen-containing functional groups than the RH-AC. Removal capacity of Pb(II) ions by the M-RH-AC and RH-AC from water solution was estimated concerning the influence of contact time, pH value, and initial concentration. The equilibrium time of Pb(II) removal was found to be around 90min after modification process. Two kinetic models are adopted to describe the possible Pb(II) adsorption mechanism, finding that the adsorption rate of Pb(II) ions by the M-RH-AC is larger than that of RH-AC.

  7. Characterisation of water hyacinth with microwave-heated alkali pretreatment for enhanced enzymatic digestibility and hydrogen/methane fermentation.

    PubMed

    Lin, Richen; Cheng, Jun; Song, Wenlu; Ding, Lingkan; Xie, Binfei; Zhou, Junhu; Cen, Kefa

    2015-04-01

    Microwave-heated alkali pretreatment (MAP) was investigated to improve enzymatic digestibility and H2/CH4 production from water hyacinth. SEM revealed that MAP deconstructed the lignocellulose matrix and swelled the surfaces of water hyacinth. XRD indicated that MAP decreased the crystallinity index from 16.0 to 13.0 because of cellulose amorphisation. FTIR indicated that MAP effectively destroyed the lignin structure and disrupted the crystalline cellulose to reduce crystallinity. The reducing sugar yield of 0.296 g/gTVS was achieved at optimal hydrolysis conditions (microwave temperature = 190°C, time = 10 min, and cellulase dosage = 5 wt%). The sequentially fermentative hydrogen and methane yields from water hyacinth with MAP and enzymatic hydrolysis were increased to 63.9 and 172.5 mL/gTVS, respectively. The energy conversion efficiency (40.0%) in the two-stage hydrogen and methane cogeneration was lower than that (49.5%) in the one-stage methane production (237.4 mL/gTVS) from water hyacinth with MAP and enzymatic hydrolysis. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Microwave Heating Modelling of a Green Smoothie. Effects on Glucoraphanin, Sulforaphane and S-Methyl Cysteine Sulphoxide Changes during Storage.

    PubMed

    Castillejo, Noelia; Martínez Hernández, Ginés Benito; Lozano Guerrero, Antonio José; Pedreño Molina, Juan Luis; Gómez, Perla A; Aguayo, Encarna; Artés, Francisco; Artés Hernández, Francisco

    2017-09-08

    The heating of a green smoothie during an innovative semi-continuous microwave treatment (MW; 9 kW for 15 s) was modelled. Thermal and dielectric properties of the samples were previously determined. Furthermore, the heating effect on the main chemopreventive compounds of the smoothie and during its subsequent storage up to 30 days at 5 or 15 °C were studied. Such results were compared to conventional pasteurization (CP; 90 °C for 45 s) while unheated fresh blended samples were used as control (CTRL). A procedure was developed to predict the temperature distribution in samples inside the MW oven with the help of numerical tools. MW-treated samples showed the highest sulforaphane formation after 20 days, regardless of the storage temperature, while its content was 2-fold reduced in CP samples. Storage of the smoothie at 5 °C is crucial for maximizing the levels of the bioactive compound S-methyl cysteine sulphoxide. The proposed MW treatment can be used by the food industry to obtain an excellent homogeneous heating of a green smoothie product retaining high levels of bioactive compounds during subsequent retail/domestic storage up to one month at 5 °C. This article is protected by copyright. All rights reserved.

  9. Microwave liver ablation: influence of hepatic vein size on heat-sink effect in a porcine model.

    PubMed

    Yu, Nam C; Raman, Steven S; Kim, Young Jun; Lassman, Charles; Chang, Xinlian; Lu, David S K

    2008-07-01

    To determine influence of hepatic vein size on perfusion-mediated attenuation in adjacent microwave thermal ablation. With approval of the institutional animal research committee, seven Yorkshire pigs underwent percutaneous (n = 2) or open (n = 5) microwave liver ablation under general anesthesia. In each, multiple ultrasound-guided, nonoverlapping thermal lesions were created within 1 cm of hepatic veins in a 5-10-minute ablation at 45 W. After euthanasia, the liver was harvested and sectioned at 0.5-cm intervals and the degree of perivascular coagulation attenuation was graded on histopathologic analysis. Correlation between venous size (small, < or =3 mm; medium, 3-6 mm; and large, >6 mm) and attenuation grade was performed with use of the Spearman rank test. In 63 of 103 sections (61%)--29 of 37 (78%) small, 27 of 48 (56%) medium, and seven of 18 (39%) large veins--the thermal injury extended to the vein wall around the entire circumference of the coagulation front without distortion of the ablation margin. In 40 of 103 sections (38.9%), varying degrees of concave distortion of perivenous ablation margins were noted, with significant correlation between vein size and heat-sink extent (P < .01). However, thermal injury extended to the vascular wall in all sections without complete circumferential sparing of liver tissue. Around two thrombosed veins, thermal lesions encased the vessels, producing paradoxically convex ablation margins. Although the heat-sink effect was significantly dependent on hepatic vein size, the majority of pathologic sections exhibited no or minimal effect. Further study is required to assess clinical implications.

  10. Deep-Blue Fluorescent Particles via Microwave Heating of Polyacrylonitrile Dispersions.

    PubMed

    Go, Dennis; Jurásková, Alena; Hoffmann, Andreas; Kapiti, Gent; Kuehne, Alexander J C

    2017-03-01

    This study presents a new method to produce fluorescent particles. Established methods are based on the incorporation of conjugated dye molecules into dielectric polymer matrices or preparation of colloids, which are composed of fluorescent conjugated polymer. By contrast, this study presents a method where dielectric polyacrylonitrile is exposed to microwave radiation leading to an intramolecular cyclization reaction producing π-conjugated segments, which fluoresce blue. During this conversion, the particles shrink in diameter but as an ensemble they retain their monodispersity. This work investigates the optimal reaction conditions and characterizes the optical properties.

  11. Survival of Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella spp. on catfish fillets exposed to microwave heating in a continuous mode.

    PubMed

    Sheen, Shiowshuh; Huang, Lihan; Sommers, Christopher

    2012-08-01

    Microwave (MW) heating using continuous power output with feedback control and a modified ingredient formulation may provide better and consistent cooking of foods. Currently, household units with build-in inverter power supply units are available. These new generation MW ovens provide continuous, adjustable output and cooking, in contrast to the traditional rectifier-based ovens that rely on the on-off mechanism for control. This study attempted to apply a feedback power control (termed as modified or "smart" MW oven) and phosphate treatment to further improve heating uniformity and enhance food quality and safety. Listeria monocytogenes (Lm, 4-strain cocktail), Escherichia coli O157:H7 (Ec, 5-strain cocktail), and Salmonella spp. (Sal, 6-strain cocktail), surface inoculated onto catfish fillets (75 × 100 × 15 mm; weight 110 g), were heated using the modified MW oven to study the inactivation of the pathogens. The sensitivity of these 3 bacteria to MW heating was in the order of Ec (most), Lm, and Sal (least). Greater than 4 to 5 log CFU reductions of Ec, Lm, or Sal counts on catfish fillet surfaces were inactivated within 2 min of 1250 W MW heating, where the fillet surface temperature increased from 10 to 20 °C to 80 to 90 °C. MW heating caused degradation of catfish fillet texture, which was noticeable as early as 10 to 15 s after the heating started, as evidenced by bumping sounds. Bumping can be significantly reduced by soaking fillets in phosphate solution. However, the results may need verification if applied in different MW ovens and/or with foods positioned away the geometric oven center. This study successfully demonstrated the feasibility of applying MW energy to eliminate foodborne pathogens on fish fillets. The results demonstrated in this report with the "smart" microwave oven design may enhance microwaveable food safety and quality, and therefore promote the microwaveable food business. © 2012 Institute of Food Technologists®

  12. Interannual and Decadal Variability of Ocean Surface Latent Heat Flux as Seen from Passive Microwave Satellite Algorithms

    NASA Technical Reports Server (NTRS)

    Robertson, Franklin R.; Jackson, Darren L.; Wick, Gary A.; Roberts, Brent; Miller, Tim L.

    2007-01-01

    Ocean surface turbulent fluxes are critical links in the climate system since they mediate energy exchange between the two fluid systems (ocean and atmosphere) whose combined heat transport determines the basic character of Earth's climate. Deriving physically-based latent and sensible heat fluxes from satellite is dependent on inferences of near surface moisture and temperature from coarser layer retrievals or satellite radiances. Uncertainties in these "retrievals" propagate through bulk aerodynamic algorithms, interacting as well with error properties of surface wind speed, also provided by satellite. By systematically evaluating an array of passive microwave satellite algorithms, the SEAFLUX project is providing improved understanding of these errors and finding pathways for reducing or eliminating them. In this study we focus on evaluating the interannual variability of several passive microwave-based estimates of latent heat flux starting from monthly mean gridded data. The algorithms considered range from those based essentially on SSM/I (e.g. HOAPS) to newer approaches that consider additional moisture information from SSM/T-2 or AMSU-B and lower tropospheric temperature data from AMSU-A. On interannual scales, variability arising from ENSO events and time-lagged responses of ocean turbulent and radiative fluxes in other ocean basins (as well as the extratropical Pacific) is widely recognized, but still not well quantified. Locally, these flux anomalies are of order 10-20 W/sq m and present a relevant "target" with which to verify algorithm performance in a climate context. On decadal time scales there is some evidence from reanalyses and remotely-sensed fluxes alike that tropical ocean-averaged latent heat fluxes have increased 5-10 W/sq m since the early 1990s. However, significant uncertainty surrounds this estimate. Our work addresses the origin of these uncertainties and provides statistics on time series of tropical ocean averages, regional space

  13. Efficacy of Microwave-Heating during Alkaline Processing of Fumonisin-Contaminated Maize

    PubMed Central

    MENDEZ-ALBORES, Abraham; CARDENAS-RODRIGUEZ, Denisse Anelem; VAZQUEZ-DURAN, Alma

    2014-01-01

    Abstract Background Fumonisins (a family of foodborne carcinogenic mycotoxins) cause health hazards to humans and animals in developing countries, and has also economic implications. Therefore, the efficacy of a novel environmental friendly nixtamalization procedure to make tortillas (the main staple food for the Mexican population) was investigated. Methods Maize contaminated with 2136.67 ng/g total fumonisins was processed into tortillas, starting with maize grits mixed with water and calcium hydroxide that was cooked in a microwave field at 2.45 GHz during 3.75 min, and steeped 3.5 h at room temperature. The steeped maize grits (nixtamal) was stone-ground into masa (maize dough), which was then used to make tortillas. Total fumonisin content was determined using monoclonal antibody columns. Results Masa contained 1998.33 ng/g total fumonisins, which represents 6.5% toxin reduction. Nevertheless, fumonisin concentration was reduced significantly in tortillas (up to 985.33 ng/g) due to the cooking process, corresponding to a cumulative toxin degradation of 54%. Tortillas were below the maximum tolerated level, considering the European Union regulatory limit for fumonisins in maize (1000 ng/g). The physicochemical and technological properties of tortillas were also considered within the acceptable margins of quality. Conclusion Microwave nixtamalization was not a feasible method to reduce fumonisin content in masa to acceptable levels; however, an effective extra-reduction occurred when masa was baking into tortillas. PMID:26060737

  14. Effects of water washing and torrefaction pretreatments on rice husk pyrolysis by microwave heating.

    PubMed

    Zhang, Shuping; Dong, Qing; Zhang, Li; Xiong, Yuanquan; Liu, Xinzhi; Zhu, Shuguang

    2015-10-01

    The influences of water washing, torrefaction and combined water washing-torrefaction pretreatments on microwave pyrolysis of rice husk samples were investigated. The results indicated that the process of combined water washing-torrefaction pretreatment could effectively remove a large portion of inorganics and improve the fuel characteristics to a certain extent. The gas products were rich in combustible compositions and the syngas quality was improved by pretreatment process. The liquid products contained less moisture content, acids and furans, while more concentrated phenols and sugars from microwave pyrolysis of rice husk after pretreatments, especially after the combined water washing-torrefaction pretreatment. Biochar, produced in high yield, has the alkaline pH (pH 8.2-10.0) and high surface area (S(BET) 157.81-267.84 m(2)/g), they have the potential to be used as soil amendments. It is noteworthy that water washing increased the pore surface area of biochar, but torrefaction reduced the pore surface area. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Efficacy of Microwave-Heating during Alkaline Processing of Fumonisin-Contaminated Maize.

    PubMed

    Mendez-Albores, Abraham; Cardenas-Rodriguez, Denisse Anelem; Vazquez-Duran, Alma

    2014-02-01

    Fumonisins (a family of foodborne carcinogenic mycotoxins) cause health hazards to humans and animals in developing countries, and has also economic implications. Therefore, the efficacy of a novel environmental friendly nixtamalization procedure to make tortillas (the main staple food for the Mexican population) was investigated. Maize contaminated with 2136.67 ng/g total fumonisins was processed into tortillas, starting with maize grits mixed with water and calcium hydroxide that was cooked in a microwave field at 2.45 GHz during 3.75 min, and steeped 3.5 h at room temperature. The steeped maize grits (nixtamal) was stone-ground into masa (maize dough), which was then used to make tortillas. Total fumonisin content was determined using monoclonal antibody columns. Masa contained 1998.33 ng/g total fumonisins, which represents 6.5% toxin reduction. Nevertheless, fumonisin concentration was reduced significantly in tortillas (up to 985.33 ng/g) due to the cooking process, corresponding to a cumulative toxin degradation of 54%. Tortillas were below the maximum tolerated level, considering the European Union regulatory limit for fumonisins in maize (1000 ng/g). The physicochemical and technological properties of tortillas were also considered within the acceptable margins of quality. Microwave nixtamalization was not a feasible method to reduce fumonisin content in masa to acceptable levels; however, an effective extra-reduction occurred when masa was baking into tortillas.

  16. A spinning thermometer to monitor microwave heating and glass transitions in dynamic nuclear polarization.

    PubMed

    Miéville, Pascal; Vitzthum, Veronika; Caporini, Marc A; Jannin, Sami; Gerber-Lemaire, Sandrine; Bodenhausen, Geoffrey

    2011-11-01

    As previously demonstrated by Thurber and Tycko, the peak position of (79)Br in potassium bromide (KBr) allows one to determine the temperature of a spinning sample. We propose to adapt the original design by using a compact KBr tablet placed at the bottom of the magic angle spinning rotor, separated from the sample under investigation by a thin disk made of polytetrafluoroethylene (or 'Teflon'®). This design allows spinning the sample up to at least 16 kHz. The KBr tablet can remain in the rotor when changing the sample under investigation. Calibration in the range of 98 < T < 320 K has been carried out in a static rotor by inserting a platinum thermometer. The accuracy is better than ± 0.9 K, even in the presence of microwave irradiation. Irradiation with 5 W microwaves at 263 GHz leads to a small temperature increase of 3.6 ± 1.4 K in either static or spinning samples. The dynamic nuclear polarization enhancement decreases with increasing temperature, in particular when a frozen glassy sample undergoes a glass transition. Copyright © 2011 John Wiley & Sons, Ltd.

  17. Evaluation of geophysical parameters measured by the Nimbus-7 microwave radiometer for the TOGA Heat Exchange Project

    NASA Technical Reports Server (NTRS)

    Liu, W. Timothy; Mock, Donald R.

    1986-01-01

    The data distributed by the National Space Science Data Center on the Geophysical parameters of precipitable water, sea surface temperature, and surface-level wind speed, measured by the Scanning Multichannel Microwave Radiometer (SMMR) on Nimbus-7, are evaluated with in situ measurements between Jan. 1980 and Oct. 1983 over the tropical oceans. In tracking annual cycles and the 1982-83 E1 Nino/Southern Oscillation episode, the radiometer measurements are coherent with sea surface temperatures and surface-level wind speeds measured at equatorial buoys and with precipitable water derived from radiosonde soundings at tropical island stations. However, there are differences between SMMR and in situ measurements. Corrections based on radiosonde and ship data were derived supplementing correction formulae suggested in the databook. This study is the initial evaluation of the data for quantitative description of the 1982-83 E1 Nino/Southern Oscillation episode. It paves the way for determination of the ocean-atmosphere moisture and latent heat exchanges, a priority of the Tropical Ocean and Global Atmosphere (TOGA) Heat Exchange Program.

  18. Metabolic effects of microwave radiation and convection heating on human mononuclear leukocytes. Final report, January 1985-May 1986

    SciTech Connect

    Kiel, J.L.; Wong, L.S.; Erwin, D.N.

    1986-01-01

    Investigated here were the effects of microwave (MW) radiation (2450-MHz, continuous-wave, mean specific absorption rate of 103.5 + or - 4.2 W/kg) and convention heating on the nonphosphorylating oxidative metabolism of human peripheral mononuclear leukocytes (96% lymphocytes, 4% monocytes) at 37 C. Metabolic activity, determined by chemiluminescence (CL) of cells challenged with luminol (5-aminO-2, 3-dihydro-1, 4-phthalazinedione) linked to bovine serum albumin, was detected with a brightness photomer. A significant stimulation after after MW exposure (p < 0.005) over total CL of matched 37 C-incubator controls was observed. A similar degree of stimulation, compared to incubator controls, was also detected after sham treatment. No significant difference existed between changes in total CL or stimulation indices of the MW and sham-exposed groups. Exposure to MW radiation, under normothermic (37 + or - 0.03 C) conditions, appears to have no effect on the oxidative metabolic activity of human peripheral mononuclear leukocytes. However, the significant differences between MW or sham-exposed cells and their respective incubator controls occurred because the temperature of the incubator did not exceed 35.9 C, and 39 minutes were required for the temperature to rise from 22 to 35.9 C. Slow heating of incubator controls must be accounted for in thermal and redio-frequency radiation studies in vitro.

  19. Intermittent microwave heating synthesized high performance spherical LiFePO{sub 4}/C for Li-ion batteries

    SciTech Connect

    Zou, Hongli; Zhang, Guanghui; Shen, Pei Kang

    2010-02-15

    An intermittent microwave heating method was used to synthesize spherical LiFePO{sub 4}/C in the presence of glucose as reductive agent and carbon source without the use of the inert gas in the oven processes. The FePO{sub 4} was used as iron precursor to reduce the cost and three lithium salts of Li{sub 2}CO{sub 3}, LiOH and CH{sub 3}COOLi were chosen for comparison of the resulting materials. The materials can be alternatively heated by this method at a temperature controllable mode for crystallization and phase transformation and to provide relaxation time for protecting particles growth. The X-ray diffraction and scanning electron microscope measurements confirmed that the LiFePO{sub 4}/C is olivine structured with the average particle size of 50-100 nm. The spherical LiFePO{sub 4}/C as cathode material showed better electrochemical performance in terms of the specific capacity and the cycling stability, which might be attributed to the highly crystallized phase, small particle distribution and improved conductivity by carbon connection.

  20. [The role of heat shock proteins HSP90 in the response of immune cells to centimeter microwaves].

    PubMed

    Glushkova, O V; Novoselova, E G; Khrenov, M O; Novoselova, T V; Cherenkov, D A; Lunin, S M; Fesenko, E E

    2008-01-01

    The effects of low-level electromagnetic waves (8.15-18 GHz, 1 microW/cm2, 1 h) on the production of heat shock proteins, several cytokines, and nitric oxide in isolated mouse macrophages and lymphocytes were examined both under normal conditions and after the treatment of the cells with geldanamycin (GA), a depressor of activity of the heat shock protein 90 (Hsp90). The irradiation of cells without GA induced the production of Hsp70, nitric oxide (NO), interleukin-1beta (IL-1beta), interleukin-10 (IL-10), and the tumor necrosis factor -alpha (TNF-alpha). No changes in the production of Hsp90 in irradiated cells were observed, but intracellular locations of Hsp25 and Hsp70 altered. The preliminary treatment of cells with GA did not remove the effects of microwaves: in these conditions, the synthesis of all cytokines tested, nitric oxide, as well as total and membrane amount of Hsp70, and the amount of Hsp25 in the cytoplasm and cytoskeleton increased. Moreover, the exposure of cells incubated with GA resulted in the reduction of Hsp90-alpha production.

  1. Volatile compounds of black cumin seeds (Nigella sativa L.) from microwave-heating and conventional roasting.

    PubMed

    Kiralan, Mustafa

    2012-04-01

    The volatile compounds in raw, conventionally roasted and microwave roasted black cumin (Nigella sativa L.) seeds at 0.45 kW for 2, 4, and 8 min, were analyzed by headspace-SPME gas chromatography-mass spectrometry. Among the 38 volatile compounds identified, the major compounds were thymoquinone and p-cymene in all samples. The levels of these compounds decreased with roasting. However, concentrations of pyrazines and furans increased significantly as a result of roasting and these compounds may affect the flavor of roasted black cumin seeds. Methyl pyrazine and 2,5-dimethylpyrazine were major pyrazines, formed at high concentration in seeds roasted for 8 min and in conventional roasting.

  2. Microwave bonding of thin film metal coated substrates

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B. (Inventor); Mai, John D. (Inventor); Jackson, Henry W. (Inventor); Budraa, Nasser K. (Inventor); Pike, William T. (Inventor)

    2004-01-01

    Bonding of materials such as MEMS materials is carried out using microwaves. High microwave absorbing films are placed within a microwave cavity containing other less microwave absorbing materials, and excited to cause selective heating in the skin depth of the films. This causes heating in one place more than another. This thereby minimizes unwanted heating effects during the microwave bonding process.

  3. Experimental measurement of microwave ablation heating pattern and comparison to computer simulations.

    PubMed

    Deshazer, Garron; Prakash, Punit; Merck, Derek; Haemmerich, Dieter

    2017-02-01

    For computational models of microwave ablation (MWA), knowledge of the antenna design is necessary, but the proprietary design of clinical applicators is often unknown. We characterised the specific absorption rate (SAR) during MWA experimentally and compared to a multi-physics simulation. An infrared (IR) camera was used to measure SAR during MWA within a split ex vivo liver model. Perseon Medical's short-tip (ST) or long-tip (LT) MWA antenna were placed on top of a tissue sample (n = 6), and microwave power (15 W) was applied for 6 min, while intermittently interrupting power. Tissue surface temperature was recorded via IR camera (3.3 fps, 320 × 240 resolution). SAR was calculated intermittently based on temperature slope before and after power interruption. Temperature and SAR data were compared to simulation results. Experimentally measured SAR changed considerably once tissue temperatures exceeded 100 °C, contrary to simulation results. The ablation zone diameters were 1.28 cm and 1.30 ± 0.03 cm (transverse), and 2.10 cm and 2.66 ± -0.22 cm (axial), for simulation and experiment, respectively. The average difference in temperature between the simulation and experiment were 5.6 °C (ST) and 6.2 °C (LT). Dice coefficients for 1000 W/kg SAR iso-contour were 0.74 ± 0.01 (ST) and 0.77 (± 0.03) (LT), suggesting good agreement of SAR contours. We experimentally demonstrated changes in SAR during MWA ablation, which were not present in simulation, suggesting inaccuracies in dielectric properties. The measured SAR may be used in simplified computer simulations to predict tissue temperature when the antenna geometry is unknown.

  4. a High-Power Microwave Transmission and Launching System for Plasma Heating on the Ornl ATF Experiment.

    NASA Astrophysics Data System (ADS)

    Bigelow, Timothy Stuart

    1990-01-01

    A high power microwave transmission and launching system has been developed for Electron Cyclotron Heating (ECH) of plasmas in the Advanced Toroidal Facility (ATF) fusion confinement experiment at Oak Ridge National Laboratory. Microwave power is generated by two 53 GHz, 200 KW cw gyrotron tubes. A waveguide transmission and launching system for each tube has been designed and built with the goal of depositing the maximum amount of power at the center of the plasma. Centralized deposition of the microwave power is possible at high frequencies by use of a launcher with a narrow radiated beamwidth and carefully controlled polarization to couple to electrons at the cyclotron resonant surface. In order for the transmission systems to operate at this high frequency and power level, highly over-moded waveguides have been used to reduce losses and arcing. To produce a narrow, polarized beam, the waveguide system was designed for minimum parasitic mode conversion so that the launcher can operate with nearly a single input mode. Several waveguide components were developed for the waveguide system including: a waveguide mode analyzing directional coupler, a rippled-wall mode converter, improved miter bends, and vacuum pumpout sections. To determine the mode purity of these components and efficiency of the system, laboratory measurement techniques for over-moded waveguide component evaluation were developed. A polarization controlled beam launcher was developed which launches a ~ 12 cm (-20 dB) beamwidth linearly polarized beam. The plane of polarization can be rotated to allow optimum coupling to either extra-ordinary or ordinary plasma waves. The transmission and launching system performed reliably. Modeling of electromagnetic wave propagation in the ATF plasma and measurement of beam absorption and plasma parameters were performed to determine the overall effectiveness of the ECH system. A coupled-mode wave propagation code was written to investigate the effect of magnetic

  5. Sustainable and Selective Separation of PVC and ABS from a WEEE Plastic Mixture Using Microwave and/or Mild-Heat Treatment with Froth Flotation.

    PubMed

    Thanh Truc, Nguyen Thi; Lee, Byeong-Kyu

    2016-10-04

    This study reports simple, selective, and sustainable separation of chlorinated plastic (polyvinyl chloride, PVC) and acrylonitrile butadiene styrene (ABS) containing brominated flame retardants (BFRs) from mixed waste electrical and electronic equipment (WEEE) plastics using microwave and/or mild-heat treatment. Microwave treatment after plastic coating with powdered activated carbon (PAC) selectively increased the hydrophilicity of the PVC surface, which facilitated PVC separation (100% recovery and purity) from the WEEE plastic mixture under the optimum flotation conditions. A further mild-heat treatment for 100 s facilitated selective separation with the highest recovery and purity (100%) of PAC-coated ABS containing BFRs from the remaining plastic mixture due to selective formation of a twisted structure with a lower density than water and the untreated ABS. Mild-heat treatment only of PAC-coated WEEE plastic mixture resulted in successful recovery of (100%) the ABS and PVC. However, the recovered PVC had slightly reduced purity (96.8%) as compared to that obtained using the combined heat and microwave treatments. The combination of both treatments with flotation facilitated selective and sustainable separation of PVC and ABS from WEEE plastics to improve their recycling quality.

  6. Microwave-Assisted Olefin Metathesis

    NASA Astrophysics Data System (ADS)

    Nicks, François; Borguet, Yannick; Sauvage, Xavier; Bicchielli, Dario; Delfosse, Sébastien; Delaude, Lionel; Demonceau, Albert

    Since the first reports on the use of microwave irradiation to accelerate organic chemical transformations, a plethora of papers have been published in this field. In most examples, microwave heating has been shown to dramatically reduce reaction times, increase product yields, and enhance product purity by reducing unwanted side reactions compared to conventional heating methods. The present contribution aims at illustrating the advantages of this technology in olefin metathesis and, when data are available, at comparing microwave-heated and conventionally heated experiments

  7. Performance of male broiler chicks exposed to heat from infrared or microwave sources

    SciTech Connect

    Morrison, W.D.; Amyot, E.; McMillan, I.; Otten, L.; Pei, D.C.

    1987-11-01

    In eight trials, 240 male broiler birds, initially 7 days old, were randomly allocated to three treatments. Treatments were: continuous infrared (CI), intermittent infrared (II; 4 min on, 2 min off, 10 cycles/h), and intermittent microwaves (IM; 2 min on, 4 min off, 10 cycles/h). At the conclusion of the 14-day experimental period the 21-day-old birds were killed. Although there were significant differences (P less than or equal to .05) in mean gain over the 2-wk treatment period between trials, no differences (P greater than .05) were attributed to treatments. There were, however, significant differences in feed:gain ratios between trials and between treatments. Feed:gain ratios of birds kept under CI and II treatments did not differ significantly (P greater than .05). However, feed:gain ratios, 1.61 +/- .04 and 1.57 +/- .04 for CI and II, respectively, differed significantly (P less than or equal to .05) from that of the IM treatment (1.76 +/- .04). The protein content of chicks under II was significantly (P less than or equal to .05) lower than that of birds under IM. There were no differences (P greater than .05) in fat, ash, calcium, and phosphorus content of chicks among treatments.

  8. Thermal analysis of an indirectly heat pulsed non-volatile phase change material microwave switch

    SciTech Connect

    Young, Robert M. El-Hinnawy, Nabil; Borodulin, Pavel; Wagner, Brian P.; King, Matthew R.; Jones, Evan B.; Howell, Robert S.; Lee, Michael J.

    2014-08-07

    We show the finite element simulation of the melt/quench process in a phase change material (GeTe, germanium telluride) used for a radio frequency switch. The device is thermally activated by an independent NiCrSi (nickel chrome silicon) thin film heating element beneath a dielectric separating it electrically from the phase change layer. A comparison is made between the predicted and experimental minimum power to amorphize (MPA) for various thermal pulse powers and pulse time lengths. By including both the specific heat and latent heat of fusion for GeTe, we find that the MPA and the minimum power to crystallize follow the form of a hyperbola on the power time effect plot. We also find that the simulated time at which the entire center GeTe layer achieves melting accurately matches the MPA curve for pulse durations ranging from 75–1500 ns and pulse powers from 1.6–4 W.

  9. Uniform batch processing using microwaves

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B. (Inventor); Jackson, Henry W. (Inventor)

    2000-01-01

    A microwave oven and microwave heating method generates microwaves within a cavity in a predetermined mode such that there is a known region of uniform microwave field. Samples placed in the region will then be heated in a relatively identical manner. Where perturbations induced by the samples are significant, samples are arranged in a symmetrical distribution so that the cumulative perturbation at each sample location is the same.

  10. High-throughput and time-resolved energy-dispersive X-ray diffraction (EDXRD) study of the formation of CAU-1-(OH)2: microwave and conventional heating.

    PubMed

    Ahnfeldt, Tim; Moellmer, Jens; Guillerm, Vincent; Staudt, Reiner; Serre, Christian; Stock, Norbert

    2011-05-27

    Aluminium dihydroxyterephthalate [Al(8)(OH)(4)(OCH(3))(8)(BDC(OH)(2))(6)]⋅x H(2)O (denoted CAU-1-(OH)(2)) was synthesized under solvothermal conditions and characterized by X-ray powder diffraction, IR spectroscopy, sorption measurements, as well as thermogravimetric and elemental analysis. CAU-1-(OH)(2) is isoreticular to CAU-1 and its pores are lined with OH groups. It is stable under ambient conditions and in water, and it exhibits permanent porosity and two types of cavities with effective diameters of approximately 1 and 0.45 nm. The crystallization of CAU-1-(OH)(2) was studied by in situ energy-dispersive X-ray diffraction (EDXRD) experiments in the 120-145 °C temperature range. Two heating methods-conventional and microwave-were investigated. The latter leads to shorter induction periods as well as shorter reaction times. Whereas CAU-1-(OH)(2) is formed at all investigated temperatures using conventional heating, it is only observed below 130 °C using microwave heating. The calculation of the activation energy of the crystallization of CAU-1-(OH)(2) exhibits similar values for microwave and conventional synthesis. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Microwave sintering of ceramics

    SciTech Connect

    Snyder, W.B.

    1989-01-01

    Successful adaptation of microwave heating to the densification of ceramic materials require a marriage of microwave and materials technologies. Using an interdisciplinary team of microwave and materials engineers, we have successfully demonstrated the ability to density ceramic materials over a wide range of temperatures. Microstructural evolution during microwave sintering has been found to be significantly different from that observed in conventional sintering. Our results and those of others indicate that microwave sintering has the potential to fabricate components to near net shape with mechanical properties equivalent to hot pressed or hot isostatically pressed material. 6 refs., 11 figs.

  12. X-ray imaging studies of electron cyclotron microwave-heated plasmas in the Tandem Mirror Experiment-Upgrade

    SciTech Connect

    Failor, B.H.

    1986-02-01

    An x-ray pinhole camera designed to efficiently detect photons with energies between 5 and 250 keV was built to image bremsstrahlung emission from a microwave-heated hot electron plasma. This plasma is formed at one of the thermal barrier locations in the Tandem Experiment-Upgrade at Lawrence Livermore National Laboratory. The instrument consists of a lead aperture, an x-ray converter in the form of a sodium-activated cesium iodide scintillator, light intensifier electronics, and a recording medium that may either be high speed film or a CCD array. The nominal spatial and temporal resolutions are one part in 40 and 17 msec, respectively. The component requirements for optimum performance were determined both analytically and by computer simulation, and were verified experimentally. The details of these results are presented. The instrument has been used to measure x-ray emission from the TMX-U west end cell. Data acquired with the x-ray camera has allowed us to infer the temporal evolution of the mirror-trapped electron radial profile.

  13. Effect of Activating Agent on the Preparation of Bamboo-Based High Surface Area Activated Carbon by Microwave Heating

    NASA Astrophysics Data System (ADS)

    Xia, Hongying; Wu, Jian; Srinivasakannan, Chandrasekar; Peng, Jinhui; Zhang, Libo

    2016-06-01

    The present work attempts to convert bamboo into a high surface area activated carbon via microwave heating. Different chemical activating agents such as KOH, NaOH, K2CO3 and Na2CO3 were utilized to identify a most suitable activating agent. Among the activating agents tested KOH was found to generate carbon with the highest porosity and surface area. The effect of KOH/C ratio on the porous nature of the activated carbon has been assessed. An optimal KOH/C ratio of 4 was identified, beyond which the surface area as well as the pore volume were found to decrease. At the optimized KOH/C ratio the surface area and the pore volume were estimated to be 3,441 m2/g and 2.093 ml/g, respectively, with the significant proportion of which being microporous (62.3%). Activated carbon prepared under the optimum conditions was further characterized using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). Activated carbons with so high surface area and pore volume are very rarely reported, which could be owed to the nature of the precursor and the optimal conditions of mixture ratio adopted in the present work.

  14. Green Synthesis of Silicon Carbide Nanowhiskers by Microwave Heating of Blends of Palm Kernel Shell and Silica

    NASA Astrophysics Data System (ADS)

    Voon, C. H.; Lim, B. Y.; Gopinath, S. C. B.; Tan, H. S.; Tony, V. C. S.; Arshad, M. K. Md; Foo, K. L.; Hashim, U.

    2016-11-01

    Silicon carbide nanomaterials especially silicon carbide nanowhiskers (SiCNWs) has been known for its excellent properties such as high thermal stability, good chemical inertness and excellent electronic properties. In this paper, a green synthesis of SiCNWs by microwave heating of blends of palm kernel shell (PKS) and silica was presented. The effect of ratio of PKS and silica on the synthesis process was also studied and reported. Blends of PKS and silica in different ratio were mixed homogenously in ultrasonic bath for 2 hours using ethanol as liquid medium. The blends were then dried on hotplate to remove the ethanol and compressed into pellets form.. Synthesis was conducted in 2.45 GHz multimode cavity at 1400 °C for 40 minutes. X-ray diffraction revealed that β-SiC was detected for samples synthesized from blends with ratio of PKS to silica of 5:1 and 7:1. FESEM images also show that SiCNWs with the average diameter of 70 nm were successfully formed from blends with ratio of PKS to silica of 5:1 and 7:1. A vapour-liquid-solid (VLS) mechanism was proposed to explain the growth of SiCNWs from blends of PKS and silica.

  15. Design of the waveguide for microwave heating of solid lithium ceramic blankets

    SciTech Connect

    Kustom, R.L.; Fendley, P.; Tidona, J.

    1985-01-01

    A description is given of the design of a dielectric-loaded waveguide for thermohydraulic testing of solid ceramic tritium breeder material in a non-nuclear environment. The dielectric-loaded waveguide provides uniform heating over module surfaces that would face a fusion reactor plasma and simulates the exponential power decay characteristic of the neutron flux over the high power region of the blankets. A 200-MHz design suitable for modules with cross section of up to 20 x 40 cm is presented.

  16. Microwave and Millimeter Wave Testing for the Inspection of the Space Shuttle Spray on Foam Insulations (SOFI) and the Acreage Heat Tiles

    NASA Technical Reports Server (NTRS)

    Zoughi, R.; Kharkovsky, S.; Hepburn, F. L.

    2005-01-01

    The utility of microwave and millimeter wave nondestructive testing and evaluation (NDT&E) methods, for testing the Space Shuttle's external he1 tank spray on foam insulation (SOFI) and the acreage heat tiles has been investigated during the past two years. Millimeter wave NDE techniques are capable of producing internal images of SOFI. This paper presents the results of testing several diverse panels with embedded voids and debonds at millimeter wave frequencies. Additionally, the results of testing a set of heat tiles are also presented. Finally, the attributes of these methods as well as the advantageous features associated with these systems are also provided.

  17. Microwave and Millimeter Wave Testing for the Inspection of the Space Shuttle Spray On Foam Insulation (SOFI) and the Acreage Heat Tiles

    NASA Astrophysics Data System (ADS)

    Zoughi, R.; Kharkovsky, S.; Hepburn, F. L.

    2006-03-01

    The utility of microwave and millimeter wave nondestructive testing and evaluation (NDT&E) methods, for testing the Space Shuttle's external fuel tank spray on foam insulation (SOFI) and the acreage heat tiles has been investigated during the past two years. Millimeter wave NDE techniques are capable of producing internal images of SOFI. This paper presents the results of testing several diverse panels with embedded voids and debonds at millimeter wave frequencies. Additionally, the results of testing a set of heat tiles are also presented. Finally, the attributes of these methods as well as the advantageous features associated with these systems are also provided.

  18. Investigation of Rapid Low-Power Microwave-Induction Heating Scheme on the Cross-Linking Process of the Poly(4-vinylphenol) for the Gate Insulator of Pentacene-Based Thin-Film Transistors.

    PubMed

    Fan, Ching-Lin; Shang, Ming-Chi; Wang, Shea-Jue; Hsia, Mao-Yuan; Lee, Win-Der; Huang, Bohr-Ran

    2017-07-03

    In this study, a proposed Microwave-Induction Heating (MIH) scheme has been systematically studied to acquire suitable MIH parameters including chamber pressure, microwave power and heating time. The proposed MIH means that the thin indium tin oxide (ITO) metal below the Poly(4-vinylphenol) (PVP) film is heated rapidly by microwave irradiation and the heated ITO metal gate can heat the PVP gate insulator, resulting in PVP cross-linking. It is found that the attenuation of the microwave energy decreases with the decreasing chamber pressure. The optimal conditions are a power of 50 W, a heating time of 5 min, and a chamber pressure of 20 mTorr. When suitable MIH parameters were used, the effect of PVP cross-linking and the device performance were similar to those obtained using traditional oven heating, even though the cross-linking time was significantly decreased from 1 h to 5 min. Besides the gate leakage current, the interface trap state density (Nit) was also calculated to describe the interface status between the gate insulator and the active layer. The lowest interface trap state density can be found in the device with the PVP gate insulator cross-linked by using the optimal MIH condition. Therefore, it is believed that the MIH scheme is a good candidate to cross-link the PVP gate insulator for organic thin-film transistor applications as a result of its features of rapid heating (5 min) and low-power microwave-irradiation (50 W).

  19. Investigation of Rapid Low-Power Microwave-Induction Heating Scheme on the Cross-Linking Process of the Poly(4-vinylphenol) for the Gate Insulator of Pentacene-Based Thin-Film Transistors

    PubMed Central

    Fan, Ching-Lin; Shang, Ming-Chi; Wang, Shea-Jue; Hsia, Mao-Yuan; Lee, Win-Der; Huang, Bohr-Ran

    2017-01-01

    In this study, a proposed Microwave-Induction Heating (MIH) scheme has been systematically studied to acquire suitable MIH parameters including chamber pressure, microwave power and heating time. The proposed MIH means that the thin indium tin oxide (ITO) metal below the Poly(4-vinylphenol) (PVP) film is heated rapidly by microwave irradiation and the heated ITO metal gate can heat the PVP gate insulator, resulting in PVP cross-linking. It is found that the attenuation of the microwave energy decreases with the decreasing chamber pressure. The optimal conditions are a power of 50 W, a heating time of 5 min, and a chamber pressure of 20 mTorr. When suitable MIH parameters were used, the effect of PVP cross-linking and the device performance were similar to those obtained using traditional oven heating, even though the cross-linking time was significantly decreased from 1 h to 5 min. Besides the gate leakage current, the interface trap state density (Nit) was also calculated to describe the interface status between the gate insulator and the active layer. The lowest interface trap state density can be found in the device with the PVP gate insulator cross-linked by using the optimal MIH condition. Therefore, it is believed that the MIH scheme is a good candidate to cross-link the PVP gate insulator for organic thin-film transistor applications as a result of its features of rapid heating (5 min) and low-power microwave-irradiation (50 W). PMID:28773101

  20. Rapid preparation of α-FeOOH and α-Fe{sub 2}O{sub 3} nanostructures by microwave heating and their application in electrochemical sensors

    SciTech Connect

    Marinho, J.Z.; Montes, R.H.O.; Moura, A.P. de; Longo, E.; Varela, J.A.; Munoz, R.A.A.; Lima, R.C.

    2014-01-01

    Graphical abstract: - Highlights: • Simple microwave method leads to the rapid formation of the goethite and hematite. • Homogenous nucleation and growth of particles are controlled by synthesis time. • Modified electrode with α-FeOOH nanoplates improved the electrochemical response. • The sample is directly heated by microwaves and its crystallization is accelerated. • Fe{sup 3+} nanostructures are promising for development of electrochemical sensors. - Abstract: α-FeOOH (goethite) and α-Fe{sub 2}O{sub 3} (hematite) nanostructures have been successfully synthesized using the microwave-assisted hydrothermal (MAH) method and by the rapid burning in a microwave oven of the as-prepared goethite, respectively. The orthorhombic α-FeOOH to rhombohedralα-Fe{sub 2}O{sub 3} structural transformation was observed by X-ray diffraction (XRD) and Raman spectroscopy results. Plates-like α-FeOOH prepared in 2 min and rounded and quasi-octahedral shaped α-Fe{sub 2}O{sub 3} particles obtained in 10 min were observed using field emission gun scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The use of microwave heating allowed iron oxides to be prepared with shorter reaction times when compared to other synthesis methods. α-FeOOH nanoplates were incorporated into graphite-composite electrodes, which presented electrocatalytic properties towards the electrochemical oxidation of ascorbic acid in comparison with unmodified electrodes. This result demonstrates that such α-FeOOH nanostructures are very promising chemical modifiers for the development of improved electrochemical sensors.

  1. Functional properties of protein isolates extracted from stabilized rice bran by microwave, dry heat, and parboiling.

    PubMed

    Khan, Saima Hafeez; Butt, Masood Sadiq; Sharif, Mian Kamran; Sameen, Ayesha; Mumtaz, Semee; Sultan, Muhammad Tauseef

    2011-03-23

    Protein isolates extracted from differently stabilized rice bran were analyzed to work out the food use potential. Bulk density remained higher for isolates obtained from heat stabilized bran, the treatments were found to have positive impact on the oil absorption properties, while the water absorption was slightly impaired owing to some possible configurational changes. Surface hydrophobicity and emulsion properties were improved with bran stabilization. Isolates exhibited better foaming properties owing to the flexible nature of protein molecules, with less intensive disulfide bonding, that were slightly affected by the stabilization treatment. Nitrogen solubility index followed a curved pattern with the least value near isoelectric point that showed an increasing trend toward basic pH, and parboiled protein isolates exhibited better gelling properties among the isolates.

  2. Gold Nanoparticle Microwave Synthesis

    SciTech Connect

    Krantz, Kelsie E.; Christian, Jonathan H.; Coopersmith, Kaitlin; Washington, II, Aaron L.; Murph, Simona H.

    2016-07-27

    At the nanometer scale, numerous compounds display different properties than those found in bulk material that can prove useful in areas such as medicinal chemistry. Gold nanoparticles, for example, display promise in newly developed hyperthermia therapies for cancer treatment. Currently, gold nanoparticle synthesis is performed via the hot injection technique which has large variability in final particle size and a longer reaction time. One underdeveloped area by which these particles could be produced is through microwave synthesis. To initiate heating, microwaves agitate polar molecules creating a vibration that gives off the heat energy needed. Previous studies have used microwaves for gold nanoparticle synthesis; however, polar solvents were used that partially absorbed incident microwaves, leading to partial thermal heating of the sample rather than taking full advantage of the microwave to solely heat the gold nanoparticle precursors in a non-polar solution. Through this project, microwaves were utilized as the sole heat source, and non-polar solvents were used to explore the effects of microwave heating only as pertains to the precursor material. Our findings show that the use of non-polar solvents allows for more rapid heating as compared to polar solvents, and a reduction in reaction time from 10 minutes to 1 minute; this maximizes the efficiency of the reaction, and allows for reproducibility in the size/shape of the fabricated nanoparticles.

  3. Microwave coupler and method

    DOEpatents

    Holcombe, C.E.

    1984-11-29

    The present invention is directed to a microwave coupler for enhancing the heating or metallurgical treatment of materials within a cold-wall, rapidly heated cavity as provided by a microwave furnace. The coupling material of the present invention is an alpha-rhombohedral-boron-derivative-structure material such as boron carbide or boron silicide which can be appropriately positioned as a susceptor within the furnace to heat other material or be in powder particulate form so that composites and structures of boron carbide such as cutting tools, grinding wheels and the like can be rapidly and efficiently formed within microwave furnaces.

  4. Microwave coupler and method

    DOEpatents

    Holcombe, Cressie E.

    1985-01-01

    The present invention is directed to a microwave coupler for enhancing the heating or metallurgical treatment of materials within a cold-wall, rapidly heated cavity as provided by a microwave furnace. The coupling material of the present invention is an alpha-rhombohedral-boron-derivative-structure material such as boron carbide or boron silicide which can be appropriately positioned as a susceptor within the furnace to heat other material or be in powder particulate form so that composites and structures of boron carbide such as cutting tools, grinding wheels and the like can be rapidly and efficiently formed within microwave furnaces.

  5. Two-weeks-sustained unresponsiveness by oral immunotherapy using microwave heated cow's milk for children with cow's milk allergy.

    PubMed

    Takahashi, Masaya; Taniuchi, Shoichiro; Soejima, Kazuhiko; Hatano, Yasuko; Yamanouchi, Sohsaku; Kaneko, Kazuanri

    2016-01-01

    Several studies have reported that oral immunotherapy (OIT) is effective for children with cow's milk (CM) allergy. These studies reported the efficacy of OIT in terms of desensitization, but did not describe sustained unresponsiveness to CM. The aim of this study was to evaluate the efficacy of the OIT protocol using microwave heated cow's milk (MH-CM) in terms of 2-weeks-sustained unresponsiveness (2-weeks-SU) and safety. Forty-eight children were enrolled in this study. Thirty-one children agreed to receive rush OIT using MH-CM (the OIT group) and another 17 children who did not want to receive rush OIT formed the untreated group. Rates of desensitization and 2-weeks-sustained unresponsiveness were compared between the two groups at 1 year after the start of OIT. We followed up these rates and safety data for another year and for longer in the OIT group. No children in the untreated group did not pass an open food challenge to CM. Of the 31 children in the OIT group, 14 (P = 0.002) achieved desensitization, and 8 (P = 0.036) achieved 2-weeks-SU to CM at 1 year from the start of OIT. Two years after the start of OIT, both the rate of desensitization and the rate of 2-weeks-SU in the OIT group significantly increased compared with the rates at 1 year (P = 0.025 and P = 0.008 respectively). The rush OIT protocol using MH-CM was effective at inducing 2-weeks-SU s to CM and had a good safety profile in children with CM allergy. Trial registration Approval number: 324, Registered 3 February 2009.

  6. Pretreatment of banana agricultural waste for bio-ethanol production: individual and interactive effects of acid and alkali pretreatments with autoclaving, microwave heating and ultrasonication.

    PubMed

    Gabhane, Jagdish; William, S P M Prince; Gadhe, Abhijit; Rath, Ritika; Vaidya, Atul Narayan; Wate, Satish

    2014-02-01

    Banana agricultural waste is one of the potential lignocellulosic substrates which are mostly un-utilized but sufficiently available in many parts of the world. In the present study, suitability of banana waste for biofuel production with respect to pretreatment and reducing sugar yield was assessed. The effectiveness of both acid and alkali pretreatments along with autoclaving, microwave heating and ultrasonication on different morphological parts of banana (BMPs) was studied. The data were statistically analyzed using ANOVA and numerical point prediction tool of MINITAB RELEASE 14. Accordingly, the optimum cumulative conditions for maximum recovery of reducing sugar through acid pretreatment are: leaf (LF) as the substrate with 25 min of reaction time and 180°C of reaction temperature using microwave. Whereas, the optimum conditions for alkaline pretreatments are: pith (PH) as the substrate with 51 min of reaction time and 50°C of reaction temperature using ultrasonication (US).

  7. Comparison of properties of sintered and sintered reaction-bonded silicon nitride fabricated by microwave and conventional heating

    SciTech Connect

    Tiegs, T.N.; Kiggans, J.O. Jr.; Lin, H.T.; Willkens, C.A.

    1994-10-01

    A comparison of microwave and conventional processing of silicon nitride-based ceramics was performed to identify any differences between the two, such as improved fabrication parameters or increased mechanical properties. Two areas of thermal processing were examined: (1) sintered silicon nitride (SSN) and (2) sintered reaction-bonded silicon nitride (SRBSN). The SSN powder compacts showed improved densification and enhanced grain growth. SRBSN materials were fabricated in the microwave with a one-step process using cost-effective raw materials. The SRBSN materials had properties appropriate for structural applications. Observed increases in fracture toughness for the microwave processed SRBSN materials were attributable to enhanced elongated grain growth.

  8. Comparison of properties of sintered and sintered reaction-bonded silicon nitride fabricated by microwave and conventional heating

    SciTech Connect

    Tiegs, T.N.; Kiggans, J.O. Jr.; Lin, H.T.

    1995-10-01

    A comparison of microwave and conventional processing of silicon nitride-based ceramics was performed to identify any differences between the two, such as improved fabrication parameters or increased mechanical properties. Two areas of thermal processing were examined: sintered silicon nitride (SSN) and sintered reaction-bonded silicon nitride (SRBSN). The SSN powder compacts showed improved densification and enhanced grain growth. SRBSN materials were fabricated in the microwave with a one-step process using cost-effective raw materials. The SRBSN materials had properties appropriate for structural applications. Observed increases in fracture toughness for the microwave processed SRBSN materials were attributable to enhanced elongated grain growth.

  9. Microwaving of normally opaque and semi-opaque substances

    DOEpatents

    Sheinberg, H.; Meek, T.T.; Blake, R.D.

    1990-07-17

    Disclosed is a method of heating small particles using microwave radiation which are not normally capable of being heated by microwaves. The surfaces of the particles are coated with a material which is transparent to microwave radiation in order to cause microwave coupling to the particles and thus accomplish heating of the particles.

  10. Microwaving of normally opaque and semi-opaque substances

    DOEpatents

    Sheinberg, Haskell; Meek, Thomas T.; Blake, Rodger D.

    1990-01-01

    Method of heating small particles using microwave radiation which are not normally capable of being heated by microwaves. The surfaces of the particles are coated with a material which is transparent to microwave radiation in order to cause microwave coupling to the particles and thus accomplish heating of the particles.

  11. A preliminary study on numerical simulation of microwave heating process for chemical reaction and discussion of hotspot and thermal runaway phenomenon

    NASA Astrophysics Data System (ADS)

    Zhao, Xiang; Huang, Kama; Yan, Liping; Yao, Yuan

    2009-04-01

    The nonlinear process of microwave heating chemical reaction is studied by means of numerical simulation. Especially, the variation of temperature in terms of space and time, as well as the hotspot and thermal runaway phenomena are discussed. Suppose the heated object is a cylinder and the incident electromagnetic (EM) wave is plane wave, the problem turns out to be a coupling calculation of 2D multi-physical fields. The integral equation of EM field is solved using the method of moment (MoM) and the thermal conduction equation is solved using a semi-analysis method. Moreover, a method to determine the equivalent complex permittivity of reactant under the heating is presented in order to perform the calculation. The numerical results for water and a dummy chemical reaction ( A) show that the hotspot is a ubiquitous phenomenon in microwave heating process. When the radius of the heated object is small, the highest temperature occurs somewhere inside the object due to the concentration of the EM wave. While the radius increases to a certain degree, the highest temperature occurs somewhere close to the surface due to the skin effect, and the whole high temperature area shows crescent-shaped. That is in accordance with basic physical principles. If the radius is kept the same in the heating process, the hotspot position of water does not change, while that of reaction A with several radius values varies. For either water or A, the thermal runaway phenomenon in which small difference of radius results in large difference of highest temperature, occurs easily when the radius is small. On the contrary, it is not evident when the radius is large. Moreover, it is notable that the highest temperature in water shows oscillating decreasing trend with the increase of radius, but in reaction A almost decreases monotonously. Further study should be performed to determine if this difference is only an occasional occurrence.

  12. Microwave Oven Observations.

    ERIC Educational Resources Information Center

    Sumrall, William J.; Richardson, Denise; Yan, Yuan

    1998-01-01

    Explains a series of laboratory activities which employ a microwave oven to help students understand word problems that relate to states of matter, collect data, and calculate and compare electrical costs to heat energy costs. (DDR)

  13. Microwave Oven Observations.

    ERIC Educational Resources Information Center

    Sumrall, William J.; Richardson, Denise; Yan, Yuan

    1998-01-01

    Explains a series of laboratory activities which employ a microwave oven to help students understand word problems that relate to states of matter, collect data, and calculate and compare electrical costs to heat energy costs. (DDR)

  14. Microwave ovens: mapping the electrical field distribution.

    PubMed

    Ng, K H

    1991-07-01

    Uniformity of electric field intensity of microwaves within the microwave oven cavity is necessary to ensure even load-heating, and is particularly important in pathology procedures where small volume irradiation is carried out. A simple and rapid method for mapping electric field distribution, using reversible thermographic paint, is described. Spatial heating patterns for various positions, and the effects of introducing dummy loads to modify heating distributions, have been obtained for a dedicated microwave processor, and comparison made with a domestic microwave oven.

  15. Disinfection of Wastewater by Microwaves.

    DTIC Science & Technology

    1980-01-01

    temperature of the cells before treatment with microwaves nor the temperature of the diluent buffer showed any effect on the rate and extent of...suspension on the sur- vival of E. coli B cells subjected to microwave treatment. 11 2. Effect of the temperature of diluent upon the survival of microwave...the surface of the material to be heated by conduction, convection, and/or radiation. While microwave energy is recognized to have bactericidal ability

  16. Microwave Ablation of Hepatic Malignancy

    PubMed Central

    Lubner, Meghan G.; Brace, Christopher L.; Ziemlewicz, Tim J.; Hinshaw, J. Louis; Lee, Fred T.

    2013-01-01

    Microwave ablation is an extremely promising heat-based thermal ablation modality that has particular applicability in treating hepatic malignancies. Microwaves can generate very high temperatures in very short time periods, potentially leading to improved treatment efficiency and larger ablation zones. As the available technology continues to improve, microwave ablation is emerging as a valuable alternative to radiofrequency ablation in the treatment of hepatic malignancies. This article reviews the current state of microwave ablation including technical and clinical considerations. PMID:24436518

  17. Practical method for choosing diluent that ensures the best temperature uniformity in the case of pharmaceutical microwave vacuum drying of a heat sensitive product.

    PubMed

    Kelen, Akos; Pallai-Varsanyi, Erzsebet; Ress, Sandor; Nagy, Tibor; Pintye-Hodi, Klara

    2006-01-01

    Microwave vacuum drying is getting more and more popular thanks to its known advantageous and unique features, but its non-uniform electric field can cause nonhomogeneous temperature distribution in the workload. The origin and effect of a generated hot-spot is influenced by the electromagnetic and thermodynamic features of the microwave system and the workload. In the case of single/one pot technology, the geometry and the construction of the microwave cavity is primarily designed for high-shear granulation. As for the workload, its composition has first-order effect on the electric field pattern. The aim of our study is to present a rational decision procedure based on basic practical experiments and the elaborated '3D layered thermography' technique to make it possible to choose the most suitable diluent to formulate a heat sensitive active pharmaceutical ingredient given its stability due to temperature distribution within the workload. Comparing two commonly used diluents, namely microcrystalline cellulose and corn starch, it was found that in the case of different actives with different acceptable temperature limits different diluents are recommended. Drying of a composition consists of an active ingredient characterized by a temperature limit of 70 degrees C. Using corn starch is safer when the workload is less endangered than when using microcrystalline cellulose. Above this temperature limit microcrystalline cellulose becomes beneficial.

  18. Heat sink effect on tumor ablation characteristics as observed in monopolar radiofrequency, bipolar radiofrequency, and microwave, using ex vivo calf liver model.

    PubMed

    Pillai, Krishna; Akhter, Javid; Chua, Terence C; Shehata, Mena; Alzahrani, Nayef; Al-Alem, Issan; Morris, David L

    2015-03-01

    Thermal ablation of liver tumors near large blood vessels is affected by the cooling effect of blood flow, leading to incomplete ablation. Hence, we conducted a comparative investigation of heat sink effect in monopolar (MP) and bipolar (BP) radiofrequency ablation (RFA), and microwave (MW) ablation devices.With a perfused calf liver, the ablative performances (volume, mass, density, dimensions), with and without heat sink, were measured. Heat sink was present when the ablative tip of the probes were 8.0 mm close to a major hepatic vein and absent when >30 mm away. Temperatures (T1 and T2) on either side of the hepatic vein near the tip of the probes, heating probe temperature (T3), outlet perfusate temperature (T4), and ablation time were monitored.With or without heat sink, BP radiofrequency ablated a larger volume and mass, compared with MP RFA or MW ablation, with latter device producing the highest density of tissue ablated. MW ablation produced an ellipsoidal shape while radiofrequency devices produced spheres.Percentage heat sink effect in Bipolar radiofrequency : Mono-polar radiofrequency : Microwave was (Volume) 33:41:22; (mass) 23:56:34; (density) 9.0:26:18; and (relative elipscity) 5.8:12.9:1.3, indicating that BP and MW devices were less affected.Percentage heat sink effect on time (minutes) to reach maximum temperature (W) = 13.28:9.2:29.8; time at maximum temperature (X) is 87:66:16.66; temperature difference (Y) between the thermal probes (T3) and the temperature (T1 + T2)/2 on either side of the hepatic vessel was 100:87:20; and temperature difference between the (T1 + T2)/2 and temperature of outlet circulating solution (T4), Z was 20.33:30.23:37.5.MW and BP radiofrequencies were less affected by heat sink while MP RFA was the most affected. With a single ablation, BP radiofrequency ablated a larger volume and mass regardless of heat sink.

  19. Heat Sink Effect on Tumor Ablation Characteristics as Observed in Monopolar Radiofrequency, Bipolar Radiofrequency, and Microwave, Using Ex Vivo Calf Liver Model

    PubMed Central

    Pillai, Krishna; Akhter, Javid; Chua, Terence C.; Shehata, Mena; Alzahrani, Nayef; Al-Alem, Issan; Morris, David L.

    2015-01-01

    Abstract Thermal ablation of liver tumors near large blood vessels is affected by the cooling effect of blood flow, leading to incomplete ablation. Hence, we conducted a comparative investigation of heat sink effect in monopolar (MP) and bipolar (BP) radiofrequency ablation (RFA), and microwave (MW) ablation devices. With a perfused calf liver, the ablative performances (volume, mass, density, dimensions), with and without heat sink, were measured. Heat sink was present when the ablative tip of the probes were 8.0 mm close to a major hepatic vein and absent when >30 mm away. Temperatures (T1 and T2) on either side of the hepatic vein near the tip of the probes, heating probe temperature (T3), outlet perfusate temperature (T4), and ablation time were monitored. With or without heat sink, BP radiofrequency ablated a larger volume and mass, compared with MP RFA or MW ablation, with latter device producing the highest density of tissue ablated. MW ablation produced an ellipsoidal shape while radiofrequency devices produced spheres. Percentage heat sink effect in Bipolar radiofrequency : Mono-polar radiofrequency : Microwave was (Volume) 33:41:22; (mass) 23:56:34; (density) 9.0:26:18; and (relative elipscity) 5.8:12.9:1.3, indicating that BP and MW devices were less affected. Percentage heat sink effect on time (minutes) to reach maximum temperature (W) = 13.28:9.2:29.8; time at maximum temperature (X) is 87:66:16.66; temperature difference (Y) between the thermal probes (T3) and the temperature (T1 + T2)/2 on either side of the hepatic vessel was 100:87:20; and temperature difference between the (T1 + T2)/2 and temperature of outlet circulating solution (T4), Z was 20.33:30.23:37.5. MW and BP radiofrequencies were less affected by heat sink while MP RFA was the most affected. With a single ablation, BP radiofrequency ablated a larger volume and mass regardless of heat sink. PMID:25738477

  20. The mineralogical phase transformation of invisible gold-concentrate by microwave heating, and enhancement of their gold leaching rate

    NASA Astrophysics Data System (ADS)

    Bak, Geonyoung; Kim, Bongju; Choi, Nagchoul; Park*, Cheonyoung

    2015-04-01

    In this study, in order to obtain the maximum Au leaching rate, an invisible gold concentrate sample was microwave-treated and a thiourea leaching experiment was performed. It is found that gold exists as invisible as a result of observation with an optical microscope and an electron microscope. As the invisible gold concentrate sample was exposed to microwave longer, its temperature and weight loss were increased together and its S content was decreased. The conditions for the maximum Au leaching rate and the fast leaching effect were a particle size of -325×400 mesh, exposure to microwave for 70 minutes, 1.0 g of thiourea, 0.0504 g of sodium sulfite and 0.425 g of ferric sulfate. However, the condition under which Au was leached out to the maximum was applied to the control sample, but its Au leaching rate was just in a range of 78% to 88%. Such results suggest that the effect of sodium sulfite and ferric sulfate was more effective in the microwave-treated sample than in the control sample. Therefore, it was confirmed that the complete and very fast Au leaching can be achieved by means of the microwave pretreatment of invisible gold concentrate.

  1. Continuous pig iron making by microwave heating with 12.5 kW at 2.45 GHz.

    PubMed

    Hara, Kyosuke; Hayashi, Miyuki; Sato, Motoyasu; Nagata, Kazuhiro

    2011-01-01

    A continuous process of pig iron making using microwave of 2.45 GHz was constructed in a microwave furnace with maximum power of 12.5 kW. Pig iron was produced from the mixed powder of magnetite ore and carbon such as coal, coke and graphite. Molten pig iron initially poured from reaction chamber after about 40 min when temperature attained over 1200 degrees C. After temperature attained at 1400 degrees C, 50 or 200 g of mixed powder was added several times in regular interval and pig iron continuously dropped out from reaction chamber. When mixed powder was supplied, temperature in reaction chamber decreased by about 200 degrees C and recovered during 5 min. Finally, the recovery time of temperature lengthened. In order to make the scale-up of the microwave furnace for iron making, it has been discussed how to improve energy efficiency and to make a preferable construction.

  2. An investigation of the thermal shock resistance of lunar regolith and the recovery of hydrogen from lunar soil heated using microwave radiation

    NASA Technical Reports Server (NTRS)

    Meek, T. T.

    1991-01-01

    The objective is to develop a better understanding of the thermal shock properties of lunar regolith sintered using 2.45 GHz electromagnetic radiation and to do a preliminary study into the recovery of bound hydrogen in lunar soil heated using 2.45 GHz radiation. During the first phase of this work, lunar simulant material was used to test whether or not microhardness data could be used to infer thermal shock resistance and later actual lunar regolith was used. Results are included on the lunar regolith since this is of primary concern and not the simulant results. They were similar, however. The second phase investigated the recovery of hydrogen from lunar regolith and results indicate that microwave heating of lunar regolith may be a good method for recovery of bound gases in the regolith.

  3. Effect of Power Levels on Inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes in Tomato Paste Using 915-Megahertz Microwave and Ohmic Heating.

    PubMed

    Kim, Sang-Soon; Sung, Hye-Jung; Kwak, Hyo-Sun; Joo, In-Sun; Lee, Jeong-Su; Ko, Gwangpyo; Kang, Dong-Hyun

    2016-09-01

    The effect of power levels on inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes in tomato paste was investigated using 915-MHz microwave heating (MW) and ohmic heating (OH). Heating uniformity, pathogen inactivation, and quality aspects were determined with 1.8-, 2.1-, 2.4-, and 3.0-kW MW and corresponding OH. GInaFit was used to analyze pathogen inactivation. The heating uniformity of MW-treated samples was inferior to that of OH-treated samples at low power levels of 1.8 to 2.4 kW but improved as the power level increased. Pathogen inactivation of MW-treated samples was significantly higher than that of OH-treated samples at low power levels of 1.8 to 2.4 kW (P < 0.05) but was not significantly different at the highest power level of 3.0 kW (P > 0.05). Quality aspects (color, pH, and lycopene content), except for L*, of MW-treated samples were not significantly degraded (P > 0.05) by increased power levels. Our results indicate that increasing power levels of MW ensures heating uniformity and microbiological safety and preserves quality aspects of tomato paste.

  4. Microwave sintering of multiple articles

    DOEpatents

    Blake, Rodger D.; Katz, Joel D.

    1993-01-01

    Apparatus and method for producing articles of alumina and of alumina and silicon carbide in which the articles are sintered at high temperatures using microwave radiation. The articles are placed in a sintering container which is placed in a microwave cavity for heating. The rates at which heating and cooling take place is controlled.

  5. Impact of Cloud Model Microphysics on Passive Microwave Retrievals of Cloud Properties. Part II: Uncertainty in Rain, Hydrometeor Structure, and Latent Heating Retrievals

    NASA Astrophysics Data System (ADS)

    Seo, Eun-Kyoung; Biggerstaff, Michael I.

    2006-07-01

    The impact of model microphysics on the retrieval of cloud properties based on passive microwave observations was examined using a three-dimensional, nonhydrostatic, adaptive-grid cloud model to simulate a mesoscale convective system over ocean. Two microphysical schemes, based on similar bulk two-class liquid and three-class ice parameterizations, were used to simulate storms with differing amounts of supercooled cloud water typical of both the tropical oceanic environment, in which there is little supercooled cloud water, and midlatitude continental environments in which supercooled cloud water is more plentiful. For convective surface-level rain rates, the uncertainty varied between 20% and 60% depending on which combination of passive and active microwave observations was used in the retrieval. The uncertainty in surface rain rate did not depend on the microphysical scheme or the parameter settings except for retrievals over stratiform regions based on 85-GHz brightness temperatures TB alone or 85-GHz TB and radar reflectivity combined. In contrast, systematic differences in the treatment of the production of cloud water, cloud ice, and snow between the parameterization schemes coupled with the low correlation between those properties and the passive microwave TB examined here led to significant differences in the uncertainty in retrievals of those cloud properties and latent heating. The variability in uncertainty of hydrometeor structure and latent heating associated with the different microphysical parameterizations exceeded the inherent variability in TB cloud property relations. This was true at the finescales of the cloud model as well as at scales consistent with satellite footprints in which the inherent variability in TB cloud property relations are reduced by area averaging.

  6. A novel method of microwave heating mixed liquid-assisted regeneration of V₂O₅-WO₃/TiO₂ commercial SCR catalysts.

    PubMed

    Qiu, Kunzan; Song, Jin; Song, Hao; Gao, Xiang; Luo, Zhongyang; Cen, Kefa

    2015-10-01

    An experimental study on the regeneration of deactivated SCR catalysts was carried out using a microwave-assisted method containing three steps of washing with mixed liquid of ethanol and water, impregnating, and drying. After the regeneration treatment, NO conversion at 320 °C increased from 39 to 90% and vanadium content increased by 62.2%, which were much higher than those regenerated by the traditional method. The more impregnated vanadium was due to the fact that the rapid evaporation of mixed liquid inside the catalyst channels led to the enlargement of surface areas by creating more pores on the catalysts. Meanwhile, with the increasing concentrations of ethanol, the heating rate of the mixed liquid increased, and the volume after complete evaporation of the mixed liquid was gradually reduced. Since higher heating rate and lager volume after the liquid evaporation could help to create more pores, therefore, when the volume ratio of ethanol/mixed solution was 20%, the catalyst obtained the maximum specific surface area, which significantly increased to ca. 123% compared with the deactivated catalyst. In addition, the catalyst dried by microwave exhibited better catalytic activity than that dried in conventional oven. Therefore, this method showed great potential in industrial applications.

  7. Plasma-assisted microwave processing of materials

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin (Inventor); Ylin, Tzu-yuan (Inventor); Jackson, Henry (Inventor)

    1998-01-01

    A microwave plasma assisted method and system for heating and joining materials. The invention uses a microwave induced plasma to controllably preheat workpiece materials that are poorly microwave absorbing. The plasma preheats the workpiece to a temperature that improves the materials' ability to absorb microwave energy. The plasma is extinguished and microwave energy is able to volumetrically heat the workpiece. Localized heating of good microwave absorbing materials is done by shielding certain parts of the workpiece and igniting the plasma in the areas not shielded. Microwave induced plasma is also used to induce self-propagating high temperature synthesis (SHS) process for the joining of materials. Preferably, a microwave induced plasma preheats the material and then microwave energy ignites the center of the material, thereby causing a high temperature spherical wave front from the center outward.

  8. A small temperature rise may contribute towards the apparent induction by microwaves of heat-shock gene expression in the nematode Caenorhabditis Elegans.

    PubMed

    Dawe, Adam S; Smith, Brette; Thomas, David W P; Greedy, Steve; Vasic, Nebojsa; Gregory, Andrew; Loader, Benjamin; de Pomerai, David I

    2006-02-01

    We have previously reported that low intensity microwave exposure (0.75-1.0 GHz CW at 0.5 W; SAR 4-40 mW/kg) can induce an apparently non-thermal heat-shock response in Caenorhabditis elegans worms carrying hsp16-1::reporter genes. Using matched copper TEM cells for both sham and exposed groups, we can detect only modest reporter induction in the latter exposed group (15-20% after 2.5 h at 26 degrees C, rising to approximately 50% after 20 h). Traceable calibration of our copper TEM cell by the National Physical Laboratory (NPL) reveals significant power loss within the cell (8.5% at 1.0 GHz), accompanied by slight heating of exposed samples (approximately 0.3 degrees C at 1.0 W). Thus, exposed samples are in fact slightly warmer (by < or =0.2 degrees C at 0.5 W) than sham controls. Following NPL recommendations, our TEM cell design was modified with the aim of reducing both power loss and consequent heating. In the modified silver-plated cell, power loss is only 1.5% at 1.0 GHz, and sample warming is reduced to approximately 0.15 degrees C at 1.0 W (i.e., < or =0.1 degrees C at 0.5 W). Under sham:sham conditions, there is no difference in reporter expression between the modified silver-plated TEM cell and an unmodified copper cell. However, worms exposed to microwaves (1.0 GHz and 0.5 W) in the silver-plated cell also show no detectable induction of reporter expression relative to sham controls in the copper cell. Thus, the 20% "microwave induction" observed using two copper cells may be caused by a small temperature difference between sham and exposed conditions. In worms incubated for 2.5 h at 26.0, 26.2, and 27.0 degrees C with no microwave field, there is a consistent and significant increase in reporter expression between 26.0 and 26.2 degrees C (by approximately 20% in each of the six independent runs), but paradoxically expression levels at 27.0 degrees C are similar to those seen at 26.0 degrees C. This surprising result is in line with other evidence

  9. Comparative Kinetic Study and Microwaves Non-Thermal Effects on the Formation of Poly(amic acid) 4,4′-(Hexafluoroisopropylidene)diphthalic Anhydride (6FDA) and 4,4′-(Hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline (BAPHF). Reaction Activated by Microwave, Ultrasound and Conventional Heating

    PubMed Central

    Tellez, Hugo Mendoza; Alquisira, Joaquín Palacios; Alonso, Carlos Rius; Cortés, José Guadalupe López; Toledano, Cecilio Alvarez

    2011-01-01

    Green chemistry is the design of chemical processes that reduce or eliminate negative environmental impacts. The use and production of chemicals involve the reduction of waste products, non-toxic components, and improved efficiency. Green chemistry applies innovative scientific solutions in the use of new reagents, catalysts and non-classical modes of activation such as ultrasounds or microwaves. Kinetic behavior and non-thermal effect of poly(amic acid) synthesized from (6FDA) dianhydride and (BAPHF) diamine in a low microwave absorbing p-dioxane solvent at low temperature of 30, 50, 70 °C were studied, under conventional heating (CH), microwave (MW) and ultrasound irradiation (US). Results show that the polycondensation rate decreases (MW > US > CH) and that the increased rates observed with US and MW are due to decreased activation energies of the Arrhenius equation. Rate constant for a chemical process activated by conventional heating declines proportionally as the induction time increases, however, this behavior is not observed under microwave and ultrasound activation. We can say that in addition to the thermal microwave effect, a non-thermal microwave effect is present in the system. PMID:22072913

  10. Comparative kinetic study and microwaves non-thermal effects on the formation of poly(amic acid) 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 4,4'-(hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline (BAPHF). Reaction activated by microwave, ultrasound and conventional heating.

    PubMed

    Tellez, Hugo Mendoza; Alquisira, Joaquín Palacios; Alonso, Carlos Rius; Cortés, José Guadalupe López; Toledano, Cecilio Alvarez

    2011-01-01

    Green chemistry is the design of chemical processes that reduce or eliminate negative environmental impacts. The use and production of chemicals involve the reduction of waste products, non-toxic components, and improved efficiency. Green chemistry applies innovative scientific solutions in the use of new reagents, catalysts and non-classical modes of activation such as ultrasounds or microwaves. Kinetic behavior and non-thermal effect of poly(amic acid) synthesized from (6FDA) dianhydride and (BAPHF) diamine in a low microwave absorbing p-dioxane solvent at low temperature of 30, 50, 70 °C were studied, under conventional heating (CH), microwave (MW) and ultrasound irradiation (US). Results show that the polycondensation rate decreases (MW > US > CH) and that the increased rates observed with US and MW are due to decreased activation energies of the Arrhenius equation. Rate constant for a chemical process activated by conventional heating declines proportionally as the induction time increases, however, this behavior is not observed under microwave and ultrasound activation. We can say that in addition to the thermal microwave effect, a non-thermal microwave effect is present in the system.

  11. Advanced microwave processing concepts

    SciTech Connect

    Lauf, R.J.; McMillan, A.D.; Paulauskas, F.L.

    1997-04-01

    The purpose of this work is to explore the feasibility of several advanced microwave processing concepts to develop new energy-efficient materials and processes. The project includes two tasks: (1) commercialization of the variable-frequency microwave furnace; and (2) microwave curing of polymeric materials. The variable frequency microwave furnace, whose initial conception and design was funded by the AIM Materials Program, allows the authors, for the first time, to conduct microwave processing studies over a wide frequency range. This novel design uses a high-power traveling wave tube (TWT) originally developed for electronic warfare. By using this microwave source, one can not only select individual microwave frequencies for particular experiments, but also achieve uniform power densities over a large area by the superposition of many different frequencies. Microwave curing of various thermoset resins will be studied because it holds the potential of in-situ curing of continuous-fiber composites for strong, lightweight components or in-situ curing of adhesives, including metal-to-metal. Microwave heating can shorten curing times, provided issues of scaleup, uniformity, and thermal management can be adequately addressed.

  12. Advanced microwave processing concepts

    SciTech Connect

    Lauf, R.J.; McMillan, A.D.; Paulauskas, F.L.

    1995-05-01

    The purpose of this work is to explore the feasibility of several advanced microwave processing concepts to develop new energy-efficient materials and processes. The project includes two tasks: (1) commercialization of the variable-frequency microwave furnace; and (2) microwave curing of polymer composites. The variable frequency microwave furnace, whose initial conception and design was funded by the AIC Materials Program, will allow us, for the first time, to conduct microwave processing studies over a wide frequency range. This novel design uses a high-power traveling wave tube (TWT) originally developed for electronic warfare. By using this microwave source, one can not only select individual microwave frequencies for particular experiments, but also achieve uniform power densities over a large area by the superposition of many different frequencies. Microwave curing of thermoset resins will be studied because it hold the potential of in-situ curing of continuous-fiber composites for strong, lightweight components. Microwave heating can shorten curing times, provided issues of scaleup, uniformity, and thermal management can be adequately addressed.

  13. A Numerical Study on Microwave Coagulation Therapy

    DTIC Science & Technology

    2013-01-01

    treated by applying localized heat to cancerous tissues, often in combination with chemotherapy or radiotherapy. Microwave coagulation therapy is one...such clinical technique for treating hepatocellular carcinoma. In the treatment, a thin microwave antenna is inserted into the cancerous tissue and...the microwave energy heats up the tumor, killing the cancer cells by producing a coagulated region. Numerical models of microwave cancer therapy have

  14. Precision timing and interlocks systems for FEL (free-electron laser) heating experiments on MTX (Microwave Tokamak Experiment)

    SciTech Connect

    Petersen, D.E. )

    1989-09-20

    A new precision timing system has been installed on the Microwave Tokamak Experiment (MTX) at Lawrence Livermore National Laboratory (LLNL). The purpose of the system is to synchronize the tokamak's plasma discharge with a 140-GHz, 2-GW microwave pulse generated by a free-electron laser (FEL). The installation involved modifying the existing sequencer system and adding Digital delay generators, three in-house-designed CAMAC modules and other components. The system controls placement of the 30-ns FEL pulse during the MTX plasma discharge. It also provides precision triggers for the microwave plasma diagnostics. These triggers are distributed over 100-Mbit/s fiber-optic links. The MTX interlock system has been expanded to provide personnel safety during FEL experiments, to protect the FEL and related equipment, and to control the path of the FEL beam starting from the FEL's output, through the beam transport system, and into the tokamak. This paper describes how the existing MTX timing and interlocks systems were upgraded to accommodate these new FEL experiments. 4 refs., 4 figs.

  15. Microwave ion source

    DOEpatents

    Leung, Ka-Ngo; Reijonen, Jani; Thomae, Rainer W.

    2005-07-26

    A compact microwave ion source has a permanent magnet dipole field, a microwave launcher, and an extractor parallel to the source axis. The dipole field is in the form of a ring. The microwaves are launched from the middle of the dipole ring using a coaxial waveguide. Electrons are heated using ECR in the magnetic field. The ions are extracted from the side of the source from the middle of the dipole perpendicular to the source axis. The plasma density can be increased by boosting the microwave ion source by the addition of an RF antenna. Higher charge states can be achieved by increasing the microwave frequency. A xenon source with a magnetic pinch can be used to produce intense EUV radiation.

  16. Conventional and Microwave Joining of Silicon Carbide Using Displacement Reactions

    NASA Technical Reports Server (NTRS)

    Kingsley, J.; Yiin, T.; Barmatz, M.

    1995-01-01

    Microwave heating was used to join Silicon Carbide rods using a thin TiC /Si tape interlayer . Microwaves quickly heated the rods and tape to temperatures where solid-state displacement reactions between TiC and Si occurred.

  17. Conventional and Microwave Joining of Silicon Carbide Using Displacement Reactions

    NASA Technical Reports Server (NTRS)

    Kingsley, J.; Yiin, T.; Barmatz, M.

    1995-01-01

    Microwave heating was used to join Silicon Carbide rods using a thin TiC /Si tape interlayer . Microwaves quickly heated the rods and tape to temperatures where solid-state displacement reactions between TiC and Si occurred.

  18. Energy filtering transmission electron microscopy immunocytochemistry and antigen retrieval of surface layer proteins from Tannerella forsythensis using microwave or autoclave heating with citraconic anhydride

    PubMed Central

    2012-01-01

    Tannerella forsythensis (Bacteroides forsythus), an anaerobic Gram-negative species of bacteria that plays a role in the progression of periodontal disease, has a unique bacterial protein profile. It is characterized by two unique protein bands with molecular weights of more than 200 kDa. It also is known to have a typical surface layer (S-layer) consisting of regularly arrayed subunits outside the outer membrane. We examined the relationship between high molecular weight proteins and the S-layer using electron microscopic immunolabeling with chemical fixation and an antigen retrieval procedure consisting of heating in a microwave oven or autoclave with citraconic anhydride. Immunogold particles were localized clearly at the outermost cell surface. We also used energy-filtering transmission electron microscopy (EFTEM) to visualize 3, 3′-diaminobenzidine tetrahydrochloride (DAB) reaction products after microwave antigen retrieval with 1% citraconic anhydride. The three-window method for electron spectroscopic images (ESI) of nitrogen by the EFTEM reflected the presence of moieties demonstrated by the DAB reaction with horseradish peroxidase (HRP)-conjugated secondary antibodies instead of immunogold particles. The mapping patterns of net nitrogen were restricted to the outermost cell surface. PMID:22984898

  19. Energy filtering transmission electron microscopy immunocytochemistry and antigen retrieval of surface layer proteins from Tannerella forsythensis using microwave or autoclave heating with citraconic anhydride.

    PubMed

    Moriguchi, K; Mitamura, Y; Iwami, J; Hasegawa, Y; Higuchi, N; Murakami, Y; Maeda, H; Yoshimura, F; Nakamura, H; Ohno, N

    2012-11-01

    Tannerella forsythensis (Bacteroides forsythus), an anaerobic Gram-negative species of bacteria that plays a role in the progression of periodontal disease, has a unique bacterial protein profile. It is characterized by two unique protein bands with molecular weights of more than 200 kDa. It also is known to have a typical surface layer (S-layer) consisting of regularly arrayed subunits outside the outer membrane. We examined the relationship between high molecular weight proteins and the S-layer using electron microscopic immunolabeling with chemical fixation and an antigen retrieval procedure consisting of heating in a microwave oven or autoclave with citraconic anhydride. Immunogold particles were localized clearly at the outermost cell surface. We also used energy-filtering transmission electron microscopy (EFTEM) to visualize 3, 3'-diaminobenzidine tetrahydrochloride (DAB) reaction products after microwave antigen retrieval with 1% citraconic anhydride. The three-window method for electron spectroscopic images (ESI) of nitrogen by the EFTEM reflected the presence of moieties demonstrated by the DAB reaction with horseradish peroxidase (HRP)-conjugated secondary antibodies instead of immunogold particles. The mapping patterns of net nitrogen were restricted to the outermost cell surface.

  20. Reduction of acrylamide and its kinetics by addition of antioxidant of bamboo leaves (AOB) and extract of green tea (EGT) in asparagine-glucose microwave heating system.

    PubMed

    Zhang, Yu; Ying, Tiejin; Zhang, Ying

    2008-03-01

    This study investigated the effect of antioxidant of bamboo leaves (AOB) and extract of green tea (EGT) on the formation and kinetics of acrylamide in an equimolar asparagine-glucose model system. The substrates spiked with AOB and EGT were microwave-heated at 180 degrees C and the acrylamide content in final reaction products was quantified by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The results showed that both AOB and EGT could effectively reduce the formation of acrylamide in an asparagine-glucose microwave heating model system and achieved a maximum reduction rate when the addition levels of AOB and EGT were both 10(-6) mg/mL reaction solution. To describe the kinetic behavior of acrylamide, a simplified kinetic model was optimized and relative kinetic rate constants were evaluated under isothermal conditions. The results indicated that the reduction effect of AOB and EGT on the acrylamide formation may partly be ascribed to the decrease of the formation rate constant (k(F)) in both AOB and EGT-spiked systems (43.4% and 32.3% of decrease, respectively, P < 0.05). The kinetic parameter k(E), which represents the elimination rate of acrylamide in both AOB and EGT-spiked systems, was not significantly different (6.9% of increase and 10.9% of decrease, respectively, P > 0.05). The results of the kinetic study indicated that addition of AOB and EGT could significantly reduce the formation rate constant (k(F)) of acrylamide, but could not significantly affect the elimination rate constant (k(E)) of acrylamide.