The effect of ultrasound on the structure and properties of the water-soluble corn hull heteroxylan

Ultrasonic irradiation of a water-soluble corn hull xylan fraction in neutral and alkaline aqueous medium has been found to produce significant changes in its molecular properties. Degradation is first manifested by a decrease in the large molar mass component under generation of polymer chains with about the same size as those of the main molar mass component. The latter is slightly shifted to the lower molar mass region only at stronger irradiation conditions. Ultrasonication of the xylan in neutral aqueous medium at high ultrasound power and/or long irradiation caused no significant changes in its sugar composition, primary structure and viscoelastic properties.     

激光诱导间质热疗中生物组织的温度场研究

激光诱导间质热疗疗效评估的前提是必须获得准确的激光在不同功率、不同照射时间的生物组织温度场分布.利用多物理场直接耦合分析软件COMSOL Multiphysics构建了在组织光学参量不变情况下的三维有限元传热模型.该模型基于Pennes生物传热方程和轴对称高斯形状的激光光束热源方程,参量针对离体猪肝组织,考虑到了生物组织热物性密度、比热和热导率随温度变化的情况.仿真获得激光功率为0.77 W、0.95 W、1.23 W,照射时间为10~90 s,径向距离0~2 mm范围和轴向距离0~4 mm范围的温度场数据集.利用拟合算法,获得了自变量为激光功率、照射时间、径向距离和轴向距离的生物组织温度场分布模型.将功率为0.88 W和1.05 W时的结果与Pennes方程结果相比较,两者误差在5%以内.     

Ultrasound-enhanced extraction of lignin from bamboo (Neosinocalamus affinis): characterization of the ethanol-soluble fractions

Bamboo was submitted to ultrasound-assisted extraction in aqueous ethanol to evaluate the effect of ultrasonic irradiation on the dissolution of lignin. In this case, the dewaxed bamboo culms were subjected to ball milling for 48 h, and then were suspended in 95% ethanol followed by ultrasonic irradiations for varied times at 20 °C to obtain ethanol-soluble fractions. The structural and thermal properties of the ethanol-soluble fractions were comparatively investigated by chemical analysis including alkaline nitrobenzene oxidation, bound carbohydrate determination, FT-IR spectra, HSQC spectra, TG, and DTA. The results showed that the yields of the ethanol-soluble fractions were between 4.29% and 4.76% for the fractions prepared with ultrasonic irradiation time ranging from 5 to 55 min, as compared to 4.02% for the fraction prepared without ultrasonic irradiation. It was found that the lignin content of the fraction increased with the increase of the ultrasonic irradiation time. There was a slight increase of the molecular weight of the lignin with the increase of the ultrasonic irradiation time. Alkaline nitrobenzene oxidation coupled with HSQC analysis indicated that the lignin in the fractions was mainly composed of G S H type units as well as minor amounts of ferulic acids. In addition, the fraction prepared with ultrasonic irradiation exhibited a slightly higher thermal stability as compared to the fraction prepared without ultrasonic irradiation.     

锅炉和加热炉的声除灰

本文用实验方法,观察和研究了声除灰现象,初步归纳出除灰效果和声压级以及除灰时间的关系。初步找到除灰的声压级阈值。文中使用了旋笛式声了除灰器,声功率1950W,气声效率18%;哨式声除灰器,声功率680W,气声效率6.8%。本文列举辽阳石化厂加热炉,装上声除灰器后,热效率提高4.8%;广州石化厂新锅炉,装声除灰器,排烟温度比设计值低2-4℃。     

Ultrasound-promoted coating of MOF-5 on silk fiber and study of adsorptive removal and recovery of hazardous anionic dye “congo red”

A metal–organic framework MOF-5 has been synthesized on silk fiber through electrostatic layer-by-layer assembly. The silk surface coating was formed via sequential dipping in an alternating bath of metal and ligand solutions at room temperature by direct mixing. SEM was used to investigate the growth of MOF-5 coating as materials for separation membrane due to their desirable properties in adsorptive removal of congo red (CR) from contaminated water. The adsorption capacity of MOF-5 is remarkable high in the liquid phase. The adsorption of CR at various concentration and contact time in spontaneous process were studied. The silk fibers containing MOF-5 open a wide field of possible applications, such as protection layers or membranes in pollution remediation wastewater and any effluent. Desorption of the dye can be carried out by using NaOH solution with more than about 50% recovery of congo red from MOF-5 coated on silk membrane filtration. In order to investigate the role of sonicating on the morphology of products, one of the reactions was performed with ultrasound irradiation and the crystal growth is completed more than other methods. The samples and adsorption of CR were characterized with SEM, powder X-ray diffraction (XRD) and UV–visible spectroscopy.     

Comparative study of lignins isolated by alkali and ultrasound-assisted alkali extractions from wheat straw.

Treatment of the dewaxed wheat straw with 0.5 M KOH at 35 degrees C for 2.5 h without ultrasonic irradiation and with ultrasound assistance for 5, 10, 15, 20, 25, 30, and 35 min resulted in a dissolution of 43.9%, 43.9%, 43.9%, 44.4%, 44.4%, 45.6%, 46.8%, and 49.1% of the original lignin, respectively. Much better results were achieved under the ultrasonic irradiation time for 35 min where nearly 50% of the original lignin was solubilized at 35 degrees C for 2.5 h. The purity of the lignin preparations isolated by alkali with ultrasound assistance was higher than that of the lignin fraction obtained by alkali without ultrasonic irradiation, and their purity increased with an increment of irradiation time between 5 and 35 min, in which the content of associated polysaccharides in the former lignin preparations (0.87-1.06%) was lower than that of the latter lignin fraction (1.16%). In addition, the lignins isolated by alkali with ultrasonic irradiation time between 5 and 30 min showed a slightly higher molecular weight and thermal stability than the lignin obtained by alkali without ultrasound assistance. No substantial differences in the main structure features between the lignin preparations isolated by alkali and ultrasound-assisted alkali extractions were found.     

Photothermal biological effects of monomeric erythrocyte using optical tweezers

The changes of mechanical properties and biological activities of monomeric erythrocytes are studied using optical tweezers micromanipulation technology. Firstly, the mechanical properties of irradiated erythrocyte membranes are obtained. Weaker power laser irradiation can delay the decay of the mechanical properties of erythrocytes and promote the biological activity of erythrocytes, while higher power laser irradiation damages erythrocytes. The stronger the laser irradiation is, the more obvious and rapid the damage will be. The temperature of the cell surface will be changed by regulating the laser power and irradiation time, so the biological functions of erythrocyte can be controlled. Secondly, the finite element simulation of the temperature change on the cell surface under the condition of laser irradiation is carried out using simulation software, and the precise temperature of the cell surface irradiated cumulatively by a laser with different powers is obtained. Finally, the processes of abscission, unfolding, and denaturation of hemoglobins in erythrocytes at different temperatures due to the photothermal effect are analyzed using the model. The mechanism of laser irradiation on the elasticity of erythrocyte membranes is also obtained.     

Low Field (10 mT) Pulsed Dynamic Nuclear Polarization

EPR irradiation by a train of inverting pulses has potential advantages over continuous-wave EPR irradiation in DNP applications; however, it has previously been used only at high field (5 T). This paper presents the design and testing of an apparatus for performing pulsed DNP experiments at 10 mT with large samples (17 ml). Experimental results using pulsed DNP with an aqueous solution of a narrow-linewidth paramagnetic probe are presented. A maximum DNP enhancement of about -36 with a train of inverting pulses (width 500 ns, repetition time 4 micros) was measured. A preliminary comparison showed that, when the same enhancement value is considered, the pulsed DNP technique requires an average power that is about three times higher than that required with the CW irradiation. However, for in vivo DNP applications it is very important to minimize the average power deposited in the sample. From the experimental results reported in this work, when considering the maximum enhancement, the pulsed technique requires only 2% of the average power necessary with the CW DNP technique. We believe that this reduction in the average power can be important for future DNP studies with large biological samples.     

纤维增强复合材料激光烧蚀效应的数值模拟

考虑材料的热解、氧化、相变及辐射和内外对流换热等物理过程,给出了激光烧蚀纤维增强复合材料的物理模型及数学模型。以碳纤维/环氧树脂复合材料为例,编程计算了材料的激光烧蚀过程,计算结果与实验结果符合得较好。计算结果表明：考虑复合材料的内对流时得到的结果更准确;较强功率密度激光辐照时,氧化对烧蚀的贡献可以忽略;功率密度一定时,烧蚀质量随时间近似为线性变化,功率密度越高,烧蚀效率越高。以辐照结束时背表面温度及烧蚀质量为目标物理量,对烧蚀过程做了参数敏感性分析,结果表明：热容及热导率对背表面温度的影响较大;树脂含量对烧蚀质量的影响较大,但其相对敏感度随激光功率密度增加而下降;激光功率密度超过1 kW/cm2时,辐射系数对烧蚀质量影响较大,但其相对敏感度随激光功率密度增加而下降。     

The effect of UV irradiation on nanocrysatlline zinc oxide thin films related to gas sensing characteristics

The effect of ultraviolet (UV) light irradiation on the nanocrystalline ZnO thin films was investigated. The degree of crystallinity, electrical conductivity, optical properties and surface properties of ZnO thin films were measured as a function of UV irradiation time. It was found that the degree of crystallinity and electrical properties of ZnO films were affected by UV irradiation, however, no noticeable change in the surface morphology was observed. The gas sensing properties of as-deposited and UV irradiated films were also measured. It was observed that the gas sensing properties were affected by the UV irradiation. The irradiation time less than 5 min has improved the sensor while the irradiation time more than 5 min degraded the sensor characteristics for a UV power density of 2.45 W cm⁻².     

电子束辐照剂量对PAN/PEO交联度的影响

对PAN/PEO凝胶(5%PAN,5%PEO)在1.0 MeV电子束下进行了不同剂量的辐照。红外光谱测量表明,PAN/PEO凝胶辐照后发生了化学交联。分析结果指出,PAN/PEO的凝胶分数随着辐照剂量的增加而不断增加;其凝胶分数增长率的变化可以分为3个阶段,即快速增加阶段(0~39kGy)、下降阶段(39~130 kGy)和稳定阶段(130 kGy)。拟合发现,引入材料刚性参数β的半经验修正方程与未考虑材料刚性的Char1esby-Pinner方程相比,更符合实际测量值(对于该配比PAN/PEO,β为0.166)。交联度-辐照剂量曲线显示,交联度随辐照剂量的增加而增加,为设计新型能功能材料中所需的固定交联度的PAN/PEO凝胶提供了辐照剂量参考值。     

Sm3+ photoreduction in BaCl2 nanophases precipitated fluoroaluminate glasses under femtosecond laser irradiation

Photoreduction of samarium-doped BaCl(2)-modified aluminofluoride glass by femtosecond laser irradiation and x-ray irradiation were investigated. Photoluminescence of samarium ions indicated that photoreduction of Sm(3+)→Sm(2+) efficiently occurred in glass samples containing more than 5 mol.% BaCl(2) after femtosecond laser irradiation, while dramatic change was not observed by x-ray irradiation. Transmission electron microscope results revealed that BaCl(2) nanophases only precipitated from glass matrix with a high BaCl(2) content by focusing femtosecond laser irradiation. Samarium ions were selectively incorporated into the precipitated nanophases, resulting in the enhancement of Sm(3+) photoreduction under lower laser power.     

云母/交联聚苯乙烯复合材料制备及沿面闪络性能

交联聚苯乙烯具有优异的电气性能、力学性能和可加工性能,已作为高压绝缘材料得到了重要应用。随着脉冲功率技术向小型化方向发展,对交联聚苯乙烯真空沿面闪络性能提出了更高要求。以苯乙烯为单体,二乙烯基苯为交联剂,偶氮二异丁腈为引发剂,采用超声波分散技术将不同质量分数的云母均匀分散于溶液体系中,通过原位自由基聚合制备出云母/交联聚苯乙烯复合材料。采用红外光谱、电子扫描显微镜等对材料组成和形貌进行了表征,采用短脉冲高压测试平台研究了云母对交联聚苯乙烯真空沿面闪络性能的影响。结果表明,当云母质量分数低于5%时,复合材料中云母为均匀分散状态,随着掺杂量进一步提升,出现了明显的团聚现象;当云母质量分数为3.5%~5%之间时,真空沿面闪络击穿电压和耐电寿命较交联聚苯乙烯得到了明显提升。     

Control of the temperature responsiveness of poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) copolymer using ultrasonic irradiation

Poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) (poly(NIPAM-co-HEMA)) is a temperature-responsive copolymer that is expected to be applicable as an advanced functional polymeric material in various fields. In this study, a novel method was developed to control the responsive temperature of poly(NIPAM-co-HEMA) using an ultrasonic polymerization technique. Initially, the behavior of the reaction was investigated using NIPAM and HEMA monomers under ultrasonic irradiation. A high ultrasonic power was found to produce a high reaction rate and low number average molecular weight of the copolymer. The polydispersity of the synthesized copolymer was approximately 1.5 for all ultrasonic powers examined. In the early stage of the reaction, the molar fraction of NIPAM in the copolymer was lower than the initial molar fraction of the monomers. It was concluded that ultrasonic irradiation affected the initiation reaction and polymer degradation, but did not affect the propagation reaction. Furthermore, the effect of the ultrasonic irradiation conditions on the temperature responsiveness of the copolymer was investigated. The lower critical solution temperature (LCST) of the copolymer was found to increase with increasing ultrasonic irradiation time. In addition, in the early stages of the reaction, the measured values of the LCST were higher than the estimated values using copolymer composition. This can be attributed to some parts of the copolymer chain possessing a higher NIPAM fraction than the overall fraction due to different reactivities of the monomers and terminated radicals. This hypothesis was indirectly verified by the synthesis of a block copolymer from the PNIPAM homopolymer and HEMA monomer.     

Effects of ultrasonic irradiation on crystallization kinetics,morphological and structural properties of zeolite FAU

In this work, NaX zeolite was synthesized and the effect of ultrasound irradiation on reaction kinetics, morphological and structural properties was investigated. Ultrasound was applied, by using a plate transducer (91.8 kHz), for the first time during the crystallization of zeolite NaX, at high temperature, varying the irradiation moment and its duration. Furthermore, ultrasound was applied after the crystallization by a horn-type transducer (20–24 kHz) at low temperature. The effects of irradiated volume (100–300 mL), sonication time (2–10 min) and ultrasound power (10–200 W) were studied with a power intensity up to 100 W/cm². It was found that the application of ultrasound during the first hour of crystallization resulted in 20% reduction of reaction time compared to a standard crystallization. Ultrasound can also reduce the agglomeration degree of the final powder by combining high power and long sonication time. After 5 min sonication time at 0.3 W/mL, the tapped density of the powder was increased by 10%, from 0.37 to 0.41 g/mL. Finally, by scanning electron microscopy (SEM) it was demonstrated that ultrasound can disrupt the agglomerates without affecting the morphology of individual crystals.     

Effect of ultrasonic irradiation on the properties and performance of biodiesel produced from date seed oil used in the diesel engine

In the present study, the effect of ultrasound irradiation on the transesterification parameters, biodiesel properties, and its combustion profiles in the diesel engine was investigated. Moreover, date seed oil (DSO) was firstly utilized in the ultrasound-assisted transesterification reaction. DSO was extracted from Zahidi type date (Phoenix dactylifera) and was esterified to reduce its Free Fatty Acid (FFA) content. Biodiesel yield was optimized in both heating methods, so that the yield of 96.4% (containing 93.5% ester) at 60 °C, with 6 M ratio of methanol/oil, 1 wt% of catalyst (NaOH) and at 90 min of reaction time was reported. The ultrasound irradiation did not influence the reaction conditions except reaction time, reduced to 5 min (96.9% yield and 91.9% ester). The ultrasonic irradiation also influenced on the physicochemical properties of DSO biodiesel and improved its combustion in the diesel engine. The analysis results related to the engine and gas emission confirmed that the ultrasound-assisted produced biodiesel has lower density and viscosity, and higher oxygen content facilitating injection of fuel in the engine chamber and its combustion, respectively. Although, B40 (biodiesel blend consisting of 40% biodiesel and 60% net diesel fuel) as a blend of both fuels presented higher CO₂ and lower CO and HC in the emissions, the DSO biodiesel produced by ultrasound irradiation presented better specifications (caused about 2-fold improvement in emissions than that of conventional method). The findings of the study confirmed the positive effect of the ultrasound irradiation on the properties of the produced biodiesel along with its combustion properties in the diesel engine, consequently reducing air pollution problems.     

Effect of ultrasound on the extractibility of corn bran hemicelluloses

Various two-step extraction procedures with and without a short application of ultrasound in the first step were used to examine the effect of sonication on the extractibility and properties of the non-cellulose components of industrial corn bran (CB). The polysaccharides recovered from the extracts of the first (FI) and second (FII) extraction step were characterised by yield and composition. Using water as extractant in the first step, similar yields of total extracted polysaccharides (FI + FII) were obtained by the short sonication treatment when compared to the classical procedures using H2O2-containing alkaline media in the first step. The yields of FI + FII showed a substantial increase (10-40%) after application of ultrasound in 1% and 5% NaOH in comparison to those of the classical procedures. The content of the neutral sugar components constituting the CB xylan varied from 65 to 88 mol% in dependence on the conditions used in the first extraction step.     

Effect of ultrasound on the structural and physiochemical properties of organosolv soluble hemicelluloses from wheat straw.

Effect of ultrasound on the yield and physiochemical properties of hemicelluloses from wheat straw using 0.5 M NaOH in 60% aqueous methanol has been comparatively studied. The results showed that applying sonication for 5, 10, 15, 20, 25, 30, and 35 min resulted in an increasing yield of hemicelluloses by 2.9%, 3.9%, 6.0%, 8.6%, 8.6%, 8.6%, and 9.2% of the original hemicelluloses, respectively, in comparison with the experiment performed without ultrasonic assistance. The hemicelluloses isolated by ultrasound-assisted extraction, showed a slightly lower molecular weight, associated lignin, and thermal stability during the first stage of decomposition, but slightly more linear as compared to the hemicelluloses obtained by classical method without ultrasonic irradiation. No substantial differences in the main structure features between the hemicellulosic preparations isolated by classical or ultrasound-assisted extractions were found.     

Intensification of alkaline delignification of sugarcane bagasse using ultrasound assisted approach

Ultrasound-assisted approach has been investigated for delignification so as to develop green and sustainable technology. Combination of NaOH with ultrasound has been applied with detailed study into effect of various parameters such as time (operating range of 15–90 min), alkali concentration (0.25 M−2.5 M), solvent loading (1:15–1:30 w/v), temperature (50–90 ˚C), power (40–140 W) and duty cycle (40–70 %) at fixed frequency of 20 kHz. The optimized operating conditions established for the ultrasonic horn were 1 M as the NaOH concentration, 1 h as treatment time, 70˚C as the operating temperature, 1:20 as the biomass loading ratio, 100 W as the ultrasonic power and 70% duty cycle yielding 67.30% as the delignification extent. Comparative study performed using conventional and ultrasonic bath assisted alkaline treatment revealed lower delignification as 48.09% and 61.55% respectively. The biomass samples were characterized by SEM, XRD, FTIR and BET techniques to establish the role of ultrasound during the treatment. The morphological changes based on the ultrasound treatment demonstrated by SEM were favorable for enhanced delignification and also the crystallinity index was more in the case of ultrasound treated material than that obtained by conventional method. Specific surface area and pore size determinations based on BET analysis also confirmed beneficial role of ultrasound. The overall results clearly demonstrated the intensification obtained due to the use of ultrasonic reactors.     

Interaction of the radiation of the high-power ytterbium-fiber laser with inhomogeneous dielectric targets

The action of the radiation of the ytterbium-fiber laser (λ = 1.07 μm) on the Nd³⁺Y₂O₃ target with nonuniform transparency in the course of the nanopowder production is studied. It is demonstrated that the laser irradiation leads to an extremely rough surface with the stalagmite roughness due to a relatively large melting depth. The resulting powder consists of two fractions. The first fraction (99% of the total mass of the powder) consists of nanoparticles with a mean size of 29 nm (BET data). The second fraction consists of micro- and submicroparticles that represent circular drops condensed from the melt and shapeless debris of the target. The peaks on the diameter distribution of the drops at 2, 8, and 80 μm are determined by different effects. The laser heating of the inhomogeneous target with the nonlinear refractive index is numerically analyzed. It is demonstrated that the melting of the target is initiated at a mean laser power of 700 W, a power density of 5.6 × 10⁵ W/cm², and an irradiation time of 150 μs.