Morphophysiological and Proteomic Responses on Plants of Irradiation with Electromagnetic Waves

Electromagnetic energy is the backbone of wireless communication systems, and its progressive use has resulted in impacts on a wide range of biological systems. The consequences of electromagnetic energy absorption on plants are insufficiently addressed. In the agricultural area, electromagnetic-wave irradiation has been used to develop crop varieties, manage insect pests, monitor fertilizer efficiency, and preserve agricultural produce. According to different frequencies and wavelengths, electromagnetic waves are typically divided into eight spectral bands, including audio waves, radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. In this review, among these electromagnetic waves, effects of millimeter waves, ultraviolet, and gamma rays on plants are outlined, and their response mechanisms in plants through proteomic approaches are summarized. Furthermore, remarkable advancements of irradiating plants with electromagnetic waves, especially ultraviolet, are addressed, which shed light on future research in the electromagnetic field.     

Dielektrische Erwärmung von Zeolithen mittels Radiowellen – Selektivität,thermo‐chromatographischer Puls und Trocknen mit Wasser

Dielectric heating with radio‐frequency energy can be applied for a wide spectrum of dry or moist zeolites. It is possible to homogeneously heat packed beds in technical scale. The energy absorption strongly varies with the zeolite type enabling selective heating of layered arrangements containing different zeolites. The specific effect of water interacting with the structural cations allows establishing pronounced temperature gradients within a packed bed with varying water content. For distinct materials such as zeolite NaY, a coupled water‐temperature pulse moving through the packed bed can be established. Potential applications for such a so‐called thermo‐chromatographic pulse range from adsorptive catalytic off‐gas cleaning to thermal regeneration of zeolites in the context of gas drying.     

Influence of reversion in compounds containing recycled natural rubber: In search of sustainable processing

The influence of rubber devulcanization by microwaves in the reversion behavior is still modestly explored in the literature. The reversion occurs due to thermal degradation of unstable crosslinkings formed during the vulcanization process. This phenomenon results in poor final mechanical properties of the artifacts. In this work, some formulations based on natural rubber (NR) with the incorporation of NR devulcanized by microwaves at different exposure times to the microwaves were vulcanized by compression molding at the same temperature and time used for the study of their vulcanization characteristics, in order to correlate the properties obtained and understand the influence of the reversion on the mechanical properties. The results showed that levels of devulcanization/degradation of the recycled phase, as well as the additional heating time influenced on the behavior of reversion and, consequently, on the mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45325.     

Kinetics of microwave‐assisted polymerization of ϵ‐caprolactone

The kinetics of polymerization of ?‐caprolactone (CL) in bulk was studied by irradiating with microwave of 350 W and frequency of 2.45 GHz with different cycle‐heating periods (30–50 s). The molecular weight distributions were determined as a function of reaction time by gel permeation chromatography. Because the temperature of the system continuously varied with reaction time, a model based on continuous distribution kinetics with time/temperature‐dependent rate coefficients was proposed. To quantify the effect of microwave on polymerization, experiments were conducted under thermal heating. The polymerization was also investigated with thermal and microwave heating in the presence of zinc catalyst. The activation energies determined from temperature‐dependent rate coefficients for pure thermal heating, thermally aided catalytic polymerization, and microwave‐aided catalytic polymerization were 24.3, 13.4, and 5.7 kcal/mol, respectively. This indicates that microwaves increase the polymerization rate by lowering the activation energy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1450–1456, 2004     

Microwave and conventional curing of thick‐section thermoset composite laminates: Experiment and simulation

In conventional processing, thermal gradients cause differential curing of thick laminates and undesirable outside‐in solidification. To reduce thermal gradients, thick laminates are processed at lower cure temperatures and heated with slow heating rates, resulting in excessive cure times. Microwaves can transmit energy volumetrically and instantaneously through direct interaction of materials with applied electromagnetic fields. The more efficient energy transfer of microwaves can alleviate the problems associated with differential curing, and the preferred inside‐out solidification can be obtained. In this work, both microwave curing and thermal curing of 24.5 mm (1 inch) thick‐section glass/epoxy laminates are investigated through the development of a numerical process simulation and conducting experiments in processing thick laminates in a conventional autoclave and a microwave furnace. Outside‐in curing of the autoclave‐processed laminate resulted in visible matrix cracks, while cracks were not visible in the microwave‐processed laminate. Both numerical and experimental results show that volumetric heating due to microwaves promotes an inside‐out cure and can dramatically reduce the overall processing time.     

Calculation of Temperatures in Microwave-Heated Two-Dimensional Ceramic Bodies

Tempertures are calculated in a ceramic material exposed to microwaves. The method entails calculation of electromagnetic fields by integral formulation and subsequent solution of the heat conduction equation for temperature in a ceramic piece. The solution of the equation is numerical and the parameters used are estimates for properties of SiC. The results include a case where the complex dielectric constant is varied with temperature The computed results demonstrate that SiC can be heated to high temperatures (1000-1500 K) and that both the temperature and the temperature gradient can be controlled by varying the power density of the micro waves and the external cooling. The results also exhibit high sensitivity of temperatures to the dimensions of the material and the orientation in which microwaves impinge on the ceramic body.     

Kettenaufbau und wärmeleitfähigkeit bei amorphen linearpolymeren

The thermal conductivity of the following homopolymers was measured or extrapolated from measurements on copolymers in the temperature range from ? 180 to + 150°C: Polymethylmethacrylate, polyethylmethacrylate, poly-n-butyl-methacrylate, polymethylacrylate, polyethylacrylate, poly-n-butylacrylate, polystyrene, polyacrylonitrile. In all cases a flat maximum at the glass transition temperature was found, if the thermal conductivity was plotted over the temperature. The thermal conductivity of polyacrylonitrile, extrapolated from measurements on copolymers of methylmethacrylate and acrylonitrile, is greater than those of the other polymers as a consequence of hydrogene bonds. If the thermal conductivity of polymethacrylates and polyacrylates is plotted over the temperature difference T — T_E, a decrease of the thermal conductivity with increasing length of the side chain will be found. Also increasing substitution of H-atoms in the polyethylene chain by Cl-atoms leads to a decrease in thermal conductivity at room temperature. By measurements on copolymers of methylmethacrylate and styrene, methylmethacrylate and methylacrylate, methylmethacrylate and acrylonitrile the thermal conductivity, plotted over the molar concentration, changes monotoneously between the values of the homopolymers of the two components. Only with copolymers of methylmethacrylate and styrene this change is linear. It may be generally concluded, that the thermal conductivity of a linear polymer, plotted over T — T_E, will decrease, if units of the chain will be substituted by units of a greater mass (e. g. with longer side-chains etc.) without change of the intermolecular forces.     

Scale Continuous Microwave Dry‐Media Reactor – Part II: Application to Waxy Esters Production

The solvent free esterification reaction between stearic acid and stearyl alcohol has been examined with a montmorillonite clay as catalyst. To aim for industrial application the system has been studied on reaction rate, product purity, catalyst behavior and water removal as function of the process conditions. To avoid an etherification side reaction and to aim for the highest reaction rate, the temperature should be strictly maintained at 170 °C. This is provided on larger scale by the application of microwave heating. Although the examined Brønsted acid clay was found to lose its catalytic activity at very low water activities, a yield of 95 % pure stearyl stearate can be obtained by simply filtering of the clay without solvent extraction or distillation. The “waxy” esterification reaction was investigated with the pilot plant continuous microwave dry‐media reactor (CMDR). The reaction time needed for 95 % yield was reduced by a factor 20–30 in comparison with industrial conventional reactors. This was due to the more homogeneous heat transfer of microwaves, which allows to reach a higher bulk temperature.     

Prospects for the application of dielectric heating processes in the pre‐treatment of oilseeds

In some branches of industry dielectric heating processes are used in a wide range of different applications like drying of agricultural products and textiles or disinfection processes in the food processing and pharmaceutical industry. This report shows potential uses of this technology for thermal pre‐treatment of oilseeds. Therefore, the basic principles of the dielectric heating mechanism and some resulting characteristics are presented in comparison to conventional heating systems. Special aspects of the application of microwaves and high‐frequency energy for thermal pre‐treatment of oilseeds are also presented. Finally, some scenarios for imaginable applications of this technology in the European oil milling industry are discussed.     

Microwave‐Assisted Chemical Reactions

This article reviews the state of the art of microwave‐assisted reactions and the influence of microwaves on mass and heat transfer. The heating behavior of representative test reactions and single substances is compared for heating with microwaves and thermal energy. Similarities and differences between convective heating and dielectric irradiation methods are discussed with regard to the yield, the selectivity, and the enantiomeric purity of the reaction products. Furthermore, prevailing problems related to the scale‐up of microwave‐assisted reactions are discussed considering the energy absorption of the substances and mixtures to be heated, and their dependence on the energy consumption and the amount of substance.     

Microstructure and thermal properties of a promising thermal barrier coating: YTaO4

High temperature gas turbine sealing can increase the thermal efficiency of a gas turbine. In this paper, monoclinic phase YTaO₄ ceramics were fabricated via solid-state reaction. Phase composition and microstructures of the high-temperature-sintered YTaO₄ ceramics were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and Raman Spectroscopy. Specific heat capacity rose gradually as temperature increased, due to volumetric expansion and phonon excitations. The thermal diffusivities and conductivities decreased significantly due to the effects of the porosity and phonon scattering. However, the thermal conductivities of the specimens were lower than that of 7–8 wt% yttria-stabilized zirconia (7-8YSZ), and YTaO₄ ceramics have better thermal stability than current (TBCs) material. The Vickers hardnesses of YTaO₄ ceramics as a function of sintering temperature were lower than that of 8YSZ, indicating YTaO₄ has better fracture toughness and thermal tolerance. The results demonstrate that YTaO₄ ceramics would be an excellent candidate for use as a thermal barrier coating material for high temperature gas turbines.     

Die thermische Bodenreinigung am Beispiel ausgewählter Sanierungsfälle

Selected cases of recycling as examples of thermal soil cleaning. The term ?contamination”? is used to describe various soil and water contaminants which may engender considerable risks for the environment and the health of man and animal. Among soil cleaning processes, thermal processes have reached the most advanced development stage. With regard to their efficiencies, they are superior to physicochemical and biological processes. Thermal soil-cleaning methods are being applied successfully on an industrial scale. The soil is heated in a rotary kiln, and the escaping gas is treated by thermal afterburning and flue gas scrubbing. The plant operated by RUT have capacities of 20–30 and 30–50 t/h respectively. Ruhrkohle's pyrolysis plant with a capacity of 7 t/h is the only German thermal plant operated on an industrial scale. RUT has set up test fields and has proven that soils may be easily recultivated after thermal treatment. The clean-up of 15 000 to 80 000 t of soil is described. The largest project carried out so far (in Bingen) involved a total order volume of approx. 28 million DM. Comprehensive safety measures and measurements in the environment as well as on the construction site guarantee the protection of the population and the people employed at the site.     

Pilot Scale Continuous Microwave Dry‐Media Reactor – Part 1: Design and Modeling

This work presents a new pilot plant continuous microwave dry‐media reactor (CMDR) for industrial chemical applications. The CMDR consists of a 6 kW conveyor microwave oven with a subsequent hot air holding section. This microwave reactor has been designed for dry media or solvent‐free reactions and can treat through‐put in the range of 10–100 kg/h. The microwave heating behavior on the small scale is analyzed and the results are used to estimate the electromagnetic field requirements on the large scale. The temperature and the electric field distribution in the reactor are modeled and experimentally validated. In the second part of this study, a “waxy” esterification reaction was investigated with the CMDR. The reaction time needed for 95% yield was reduced by a factor of 20–30 compared to conventional industrial reactors. This was due to the more homogeneous heat transfer of microwaves, which allows a higher bulk temperature to be reached.     

微波在无机合成中的应用

介绍了微波的作用机理和特点，同时综述了微波在催化材料的合成过程中以及在合成纳米材料时的热处理方面有着传统加热方法无可比拟的优势，并介绍了微波烧结方法在陶瓷工业方面的应用，最后对微波在无机合成中的应用前景作了展望。     

Improvement of thermal stability and gamma-ray absorption in microwave absorbable poly(methyl methacrylate)/graphene nanoplatelets nanocomposite

The graphene nanofiller (2 wt%) was dispersed in poly(methyl methacrylate) by in situ polymerization method. The optimum high frequency (microwave) absorption was evaluated at X-band due to changes in the scattering parameters (determined by using a vector network analyzer). The slight improvement has been attained in gamma attenuation coefficient of the polymer nanocomposite by using gamma transmission technique. The addition of graphene nanoplatelets (2 wt%) resulted in a thermal improvement from 196.73 to 243.00°C (with 5% weight loss) in TGA analysis. The graphene nanoplatelets provided an optimum decrease in scattering of the microwaves due to the elimination of the defects and the prevention of the agglomeration of the graphene nanoplates. The improvement of microwave absorption (between 8 and 12 GHz) suggested that the nanocomposite was a suitable candidate as a microwave absorbing material. This multipurpose nanocomposite has provided thermal stability and it has ensured the optimum gamma-ray and microwave absorption depending on the development of the structural properties. The development of these physical characteristics has enabled to improve the electrical conductivity as a result of the progress in the structural properties.     

A Thermostat with Short- and Long-Term Stability of ± 1.5×10−4°C

The design of a thermostat which gives a temperature stability of ± 1.5 × 10^?4°C over a period of weeks is described. The temperature sensors are thermistors stabilized by heat treatment. Heat input derives mainly from stirring and heat output mainly from losses to the surroundings. Residual heat input is removed by stabilized circulating thermostats. Temperature balance is due to spread out bare wire heaters which carry a current proportional to the state of the control DC Wheatstone bridge. The controlling thermistors are maintained in two oil baths and the state of the current in the control heaters is transmitted to the thermistors by a thermal feedback system involving small heating coils which are placed in the oil baths around the thermistors and which carry a current proportional to the heating current.     

Regenerierung von Trockenmitteln für Wasserstoff durch dielektrische Erwärmung mit Radiowellen

Fine drying plays a key role for the use and especially the feeding of hydrogen into the natural gas infrastructure. For thermal regeneration of the desiccant, radio waves can be used for direct dielectric heating of the packed bed. Depending on the zeolite used, NaX or NaY, both homogeneous heating and selective heating of the water-laden desiccant beds are possible. Drying reactors were designed and successfully tested based on the technology, so that an operational pressure-resistant prototype is now available for hydrogen drying.     

On the Role of Water in Dielectric Heating with Radio Waves

Beside the classical mechanism of orientation polarization which is sufficient to explain dielectric heating of aqueous liquids, a number of additional aspects have to be considered when humid solids are heated by microwaves or radio waves. The large relative dielectric constant of water can lead to shielding and, therefore, attenuation of the electrical field in humid matrices. The shielding effect is influenced by the geometric arrangement of compartments with varying humidity. On the other hand, the large dielectric loss of water results in an effective heating. As shown by modeling of appropriate experiments, the dielectric loss factor is significantly changed for water which is in intimate contact with surfaces. The dielectric loss factor is much larger for water in the surface layers compared with the bulk phase. For some solids dielectric heating is based on a completely different mechanism which is also influenced by water. The dominant mechanism leading to dielectric heating of zeolites is the migration of cations within the zeolite framework. Water has a strong effect on the dielectric loss factor, most likely by hydration or modifying the electrostatic interactions of cations with the lattice.     

二氧化硅气凝胶高温稳定性研究

二氧化硅气凝胶具有极高的孔隙率和非常低的热导率,在保温隔热领域应用前景十分广阔。探究了二氧化硅气凝胶在不同温度热处理条件下热导率的变化情况,并从微观结构角度解释了其变化机理。随着热处理温度升高,气凝胶热导率先降低后升高。当热处理温度低于400 ℃时,气凝胶的热导率随热处理温度的升高而降低,这是因为较低温度的热处理去除了气凝胶内部的大部分杂质,并且使气凝胶的内部孔隙结构更加均匀;当热处理温度处于400~700 ℃时,更高温度的热处理使得气凝胶内部的孔径明显增大,气凝胶颗粒增大,使得热导率随热处理温度的升高而增加;当热处理温度高于700 ℃时,气凝胶颗粒开始烧结,骨架结构坍塌,密度显著增大,热导率也急剧上升,此时已不具备气凝胶轻质多孔的典型特征,可以认为已经失效。实验结果对亲水型气凝胶的应用给出了一定的指导:为保证气凝胶绝热能力的最优化,可以对气凝胶在400 ℃的温度下进行一段时间的保温;工作温度应在700 ℃以下,温度的升高会轻微降低气凝胶的隔热能力;气凝胶在700 ℃以上时会失去其绝热能力,因此不宜用于温度高于700 ℃的环境。     

A computational analysis of the heating of glass mat thermoplastic (GMT) sheets by dual beam microwave sources

The use of dual beam microwaves to heat glass mat thermoplastic has been investigated numerically using a finite difference technique, known as the alternating difference implicit (ADI) method. The variation in thermophysical properties throughout the GMT has been accounted for using a table look-up procedure, which provides the appropriate thermophysical properties for the thermal conditions at each mesh point. The use of dual beam microwaves has been shown to significantly reduce the heating times under all geometric conditions, material variations, and glass loadings. Sheet thicknesses were varied from 1 to 12 mm, glass loadings from zero to 40 wt% polypropylene, polycarbonate and nylon were all simulated. The computations indicate a clear advantage in heating times when dual beam microwave heating sources are emplyed.