Quantification of high-power ultrasound induced damage on potato starch granules using light microscopy

A simple light microscopic technique was developed in order to quantify the damage inflicted by high-power low-frequency ultrasound (0-160 W, 20 kHz) treatment on potato starch granules in aqueous dispersions. The surface properties of the starch granules were modified using ethanol and SDS washing methods, which are known to displace proteins and lipids from the surface of the starch granules. The study showed that in the case of normal and ethanol-washed potato starch dispersions, two linear regions were observed. The number of defects first increased linearly with an increase in ultrasound power up to a threshold level. This was then followed by another linear dependence of the number of defects on the ultrasound power. The power threshold where the change-over occurred was higher for the ethanol-washed potato dispersions compared to non-washed potato dispersions. In the case of SDS-washed potato starch, although the increase in defects was linear with the ultrasound power, the power threshold for a second linear region was not observed. These results are discussed in terms of the different possible mechanisms of cavitation induced-damage (hydrodynamic shear stresses and micro-jetting) and by taking into account the hydrophobicity of the starch granule surface.     

Biodiesel production process intensification using a rotor-stator type generator of hydrodynamic cavitation

Triglyceride transesterification for biodiesel production is a model reaction which is used to compare the conversion efficiency, yield, reaction time, energy consumption, scalability and cost estimation of different reactor technology and energy source. This work describes an efficient, fast and cost-effective procedure for biodiesel preparation using a rotating generator of hydrodynamic cavitation (HC). The base-catalyzed transesterification (methanol/sodium hydroxide) has been carried out using refined and bleached palm oil and waste vegetable cooking oil. The novel HC unit is a continuous rotor-stator type reactor in which reagents are directly fed into the controlled cavitation chamber. The high-speed rotation of the reactor creates micron-sized droplets of the immiscible reacting mixture leading to outstanding mass and heat transfer and enhancing the kinetics of the transesterification reaction which completes much more quickly than traditional methods. All the biodiesel samples obtained respect the ASTM standard and present fatty acid methyl ester contents of >99% m/m in both feedstocks. The electrical energy consumption of the HC reactor is 0.030 kW h per L of produced crude biodiesel, making this innovative technology really quite competitive. The reactor can be easily scaled-up, from producing a few hundred to thousands of liters of biodiesel per hour while avoiding the risk of orifices clogging with oil impurities, which may occur in conventional HC reactors. Furthermore it requires minimal installation space due to its compact design, which enhances overall security.     

Regge closed string scattering and its implication on fixed angle closed string scattering

We calculate the complete closed string high energy scattering amplitudes (HSA) in the Regge regime for arbitrary mass levels. As an application, we deduce the complete ratios among closed string HSA in the fixed angle regime by using Stirling number identities. These results are in contrast with the incomplete set of closed string HSA in the fixed angle regime calculated previously. The complete forms of the fixed angle amplitudes, and hence the ratios, were not calculable previously without the input of zero-norm state calculation. This is mainly due to the lack of saddle point in the fixed angle closed string calculation.     

Sonoelectrocatalytic decomposition of methylene blue using Ti/Ta2O5–SnO2 electrodes

Sonoelectrochemical decomposition of organic compounds is a developing technique among advanced oxidation processes (AOPs). It has the advantage over sonication alone that it increases the efficiency of the process in terms of a more rapid decrease in chemical oxygen demand (COD) and in total organic carbon (TOC) and accelerates electrochemical oxidation which normally requires a lengthy period of time to achieve significant mineralisation. Moreover the use of an electrocatalytic electrode in the process further accelerates the oxidation reaction rates. The aim of this study was to improve the decomposition efficiency of methylene blue (MB) dye by sonoelectrochemical decomposition using environmentally friendly and cost-effective Ti/Ta₂O₅–SnO₂ electrodes. Decolourisation was used to assess the initial stages of decomposition and COD together with TOC was used as a measure of total degradation. The effect of a range of sonication frequencies 20, 40, 380, 850, 1000 and 1176 kHz at different powers on the decolourisation efficiency of MB is reported. Frequencies of 850 and 380 kHz and the use of higher powers were found more effective towards dye decolourisation. The time for complete MB degradation was reduced from 180 min using electrolysis and from 90 min while carrying out sonolysis to 45 min when conducting a combined sonoelectrocatalytic experiments. The COD reduction of 85.4% was achieved after 2 h of combined sonication and electrolysis which is a slightly higher than after a single electrolysis (78.9%) and twice that of sonolysis (40.4%). A dramatic improvement of mineralisation values were observed within 2 h of sonoelectrocatalytic MB degradation. The TOC removal efficiency increased by a factor of 10.7 comparing to sonication alone and by a factor of 1.5 comparing to the electrolytic process. The energy consumption (kWh/m³) required for the complete degradation of MB was evaluated.     

Sonochemical modification of carbon nanotubes for enhanced nanocomposite performance

Multi-walled carbon nanotubes (CNTs) have been treated using 20 kHz ultrasound in combination with dilute nitric and sulfuric acids at much lower concentrations than previously reported. The measurements revealed an optimum set of sonication conditions (in this case 30 min at 12 W cm⁻²) exists to overcome aggregation of the nanotubes and to allow efficient dispersion in ethanol or in chitosan. Transmission electron microscopy and Raman spectroscopy suggested the removal of amorphous material and reduction of the CNT diameter as well as modifications to their defect structures. The surface oxidation was determined by FTIR spectroscopy. At longer times or higher ultrasound intensities, degradation such as nanotube shortening and additional defect generation in the graphitic network occurred and the benefits of using ultrasound decreased. The modified CNTs were used as fillers for chitosan films and gave a tenfold increase in tensile strength and integrity of the films. The methodology was combined with sonochemical generation of gold or iron oxide nanoparticles to produce a range of functional membranes for catalytic reductive hydrogenation or dye degradation under conditions that are more environmentally benign than those previously used. Our results further add to the usefulness of sonochemistry as a valuable tool in preparative materials chemistry but also illustrate the crucial importance of careful control over the experimental conditions if optimum results are to be obtained.     

Palm oil hydrolysis catalyzed by lipases under ultrasound irradiation--the use of experimental design as a tool for variables evaluation

Diacylglycerol oil has been increasingly recognized by its good nutritional properties and therefore, different technologies have been developed for obtaining it. The present work focuses on the diacylglycerol production by hydrolysis reaction of the palm oil using the PS IM and TL IM commercial lipases as biocatalysts under ultrasound irradiation. An experimental design (central composite rotatable design - CCRD) adopting surface response was applied as a tool to evaluate the optimal reaction conditions beyond a restrict number of experiments. Reactions were performed in an ultrasound equipment and different variables were investigated, such as temperature (30-55 °C), enzyme content (1-2 wt.% of oil mass), mechanical stirring (300-700 rpm) and reaction time. Both, PS IM and TL IM enzymes showed the best results after 1 h and 30 min of reaction under 30 °C and, applying 300 rpm as stirring. On these conditions, the diacylglycerol yield was around 34% and 39%, respectively; considering that 1% PS IM was applied for the first one and, 2% TL IM for the second one. Therefore, it was obtained good yield of a diacylglycerol-rich oil in shorter reaction times under sonication and soft conditions. The mathematic model proposed suggested a satisfactorily representation of the process and good correlation among the experimental results and the theoretical values predicted by the model equation were achieved.     

Investigation of intrinsic plasmon energy losses associated with the Fe 1s core level in metallic iron

A recently developed Cu Kα₁ (hν = 8047.8 eV) X-ray source/ESCA300 electron spectrometer combination has been used to investigate the intrinsic plasmon energy losses associated with the Fe 1s core level (binding energy = 7111 eV) in metallic iron. The surface and bulk intrinsic plasmon energy losses were separated and it was found that using the theoretically calculated extrinsic energy loss cross-section to represent the bulk intrinsic energy loss cross-section gave an overall intrinsic loss probability which is approximately the same as if a Lorentzian type cross-section is used. However, this approach does not separate the surface and bulk intrinsic losses properly and is not a good approximation for peak shape analysis in the near peak region. A more realistic approximation is provided by using a Lorentzian type energy loss cross-section to represent the bulk intrinsic energy losses. It has also been shown that for the Fe 1s core level of metallic iron the probability that a photoelectron will suffer an intrinsic energy loss is higher at the surface than in the bulk. Also for this core level the excitation probability for the intrinsic plasmons is greater than that of the extrinsic plasmons. Hence ignoring the intrinsic plasmons would cause considerable error in peak shape analysis in the near peak region.     

高能激光能量计校准方法研究

给出了一种绝对式高能激光能量计光电校准方法.该方法以大功率灯作为校准光源,通过测量灯两端的电压以及电流获得电能值,去掉灯所消耗的热能,得到灯所发出的光能.所设计平板能量计将大功率灯密封在高能激光能量计内,光能全部被能量计吸收.根据能量计输出值以及光能值便可实现能量计光电校准.结果表明,能量计光电校准不确定度约为1.5%.     

Endogenous magnetic reconnection and associated high energy plasma processes

An endogenous reconnection process involves a driving factor that lays inside the layer where a drastic change of magnetic field topology occurs. A process of this kind is shown to take place when an electron temperature gradient is present in a magnetically confined plasma and the evolving electron temperature fluctuations are anisotropic. The width of the reconnecting layer remains significant even when large macroscopic distances are considered. In view of the fact that there are plasmas in the Universe with considerable electron thermal energy contents this feature can be relied upon in order to produce generation or conversion of magnetic energy, high energy particle populations and momentum and angular momentum transport.