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1.
Wash water is circulated for use in the minimal processing industry, and inefficient disinfection methods can lead to pathogen cross-contamination. Moreover, few disinfection strategies are available for ready-to-eat fruits that do not need to be cut. In this study, the use of chlorine and ultrasound, two low-cost disinfection methods, were evaluated to disinfect winter jujube, a delicious, nutritious, and widely sold fruit in China. Ultrasound treatment (28 kHz) alone could not decrease the cross-contamination incidence of Escherichia coli O157:H7, non-O157 E. coli, and Salmonella Typhimurium, and free chlorine treatment at 10 ppm decreased the incidence from 55.00% to 5.00% for E. coli O157:H7, 65.00% to 6.67% for non-157 E. coli, and 70.00% to 6.67% for S. Typhimurium. The cross-contamination incidence was completely reduced (pathogens were not detected in sample) when the treatments were combined. The counts of aerobic mesophiles, aerobic psychrophiles, molds, yeasts, and three pathogens in the group subjected to combination treatment (28 kHz ultrasound + 10 ppm free chlorine) were significantly lower than those in the control, chlorine-treated, and ultrasound-treated groups during storage (0–7 d at 4 °C). Analysis of weight loss, sensory quality (crispness, color, and flavor), instrument color (a*/b*), soluble matter contents (total soluble solids, reducing sugar, total soluble sugar, and titratable acid), and nutritional properties (ascorbic acid and polyphenolic contents) indicated that treatment with ultrasound, chlorine, and their combination did not lead to additional quality loss compared with properties of the control. Additionally, the activities of phenylalanine ammonia-lyase and polyphenol oxidase were not significantly increased in the treatment group, consistent with the quality analysis results. These findings provide insights into disinfection of uncut ready-to-eat fruits using a minimum dose of disinfectant for cross-contamination prevention under ultrasonication. The use of ultrasound alone to decontaminate fresh produce is accompanied by a high risk of pathogen contamination, and the use of sanitizers to decrease cross-contamination incidence is recommended. 相似文献
2.
With rising consumer demand for natural products, a greener and cleaner technology, i.e., ultrasound-assisted extraction, has received immense attention given its effective and rapid isolation for nanocellulose compared to conventional methods. Nevertheless, the application of ultrasound on a commercial scale is limited due to the challenges associated with process optimization, high energy requirement, difficulty in equipment design and process scale-up, safety and regulatory issues. This review aims to narrow the research gap by placing the current research activities into perspectives and highlighting the diversified applications, significant roles, and potentials of ultrasound to ease future developments. In recent years, enhancements have been reported with ultrasound assistance, including a reduction in extraction duration, minimization of the reliance on harmful chemicals, and, most importantly, improved yield and properties of nanocellulose. An extensive review of the strengths and weaknesses of ultrasound-assisted treatments has also been considered. Essentially, the cavitation phenomena enhance the extraction efficiency through an increased mass transfer rate between the substrate and solvent due to the implosion of microbubbles. Optimization of process parameters such as ultrasonic intensity, duration, and frequency have indicated their significance for improved efficiency. 相似文献
3.
A novel, green and eco-friendly, cost-effective, fast, and reliable high energy ultrasonication (US) extraction with UHPLC-MSMS (Ultrahigh performance liquid chromatography with mass spectrometry) quantification of Glycyrrhizic acid (GZA) is reported herein for the first time. The study provides useful insights regarding the effect of US-factors with statistical analysis and mechanisms, involved in GZA-extraction and analysis. An US-extraction method (US-MD) was developed using three levels of US factors: solvents (AC (acetone), EtOH (ethanol), H2O (water)), time (1, 2, 3 min), amplitudes (30, 40, 50%), pulse (10/0.5, 20/0.5, 30/0.5 sec), particle sizes (0.5, 1, 1.4 mm), and temperatures (20, 30, 40 °C). The US-MD was further validated with high accuracy 98.96 ± 6.82 and r2 = 0.995 whereas, an in-house analytical method (UHPLC-MSMS) was developed and validated to quantify the GZAamount. UHPLCMSMS-MD resulted in a retention time of 0.31 min with MSMS (821.400 > 351.200) in a 1 min run time whereas, UHPLCMSMS-MV showed high accuracy and precision with r2 = 0.998 for GZA. Statistical analysis of K-mean clustering finalized US-set-of-factors showing optimum extract yield (mg/1mg) of 0.48 with sum (2.41 ± 014) and mean (0.27) along with a high GZA-amount (μg/mg) of 8.23 with sum (43.31 ± 2.07) and mean (4.81) for H2O in 3 min at 40 °C using particle size (1.4 mm), amplitude (50%), and pulse (30/0.5). Large scale application of US-UHPLCMSMS confirmed the evaluation power of the method showing the order for GZA amount; Egypt > Pakistan > Syria > India > Palestine > America > Georgia > Morocco. A significant effect for US factors Vs extract yield and GZA amount was observed however, solvent*GZA-amount and extract yield*particle size were more significantly correlated compared to time*temperature*amplitude*pulse analyzed via PCA, GLM-UniANOVA, K-mean, and Pearson’s correlation (P ≤ 0.05). A combined mechanism of shear stress, macroturbulence due to acoustic cavitation and implosions, sonochemical, and sonocapillary effect were noted for the US technique producing higher extract yield and GZA amount from licorice. 相似文献
4.
The exceptional properties of graphene and its structural uniqueness can improve the performance of nanocomposites if it can attain the uniform dispersion. Tip sonication assisted graphene solvent dispersion has been emerged as an efficient approach but it can cause significant degradation of graphene structure. This study aimed to evaluate the parametric influence of tip sonication on the characteristics of sp2 carbon structure in graphene nanoplatelets by varying the sonication time and respective energy at three different amplitudes (60%, 80% and 100%). The study is essential to identify appropriate parameters so as to achieve high-quality and defect-free graphene with a highly desirable aspect ratio after solvent dispersion for composite reinforcement. Quantitative approach via Raman spectroscopy is used to find the defect ratio and lateral size of graphene evolved under the effect of tip sonication parameters. Results imply that the defect ratio is steady and increases continually with GNPs, along with the transformation to the nano-crystalline stage I up to 60 min sonication at all amplitudes. Exfoliation was clearly observed at all amplitudes together with sheet re-stacking due to considerable size reduction of sheets with large quantity. Finally, considerable GNPs fragmentation occurred during sonication with increased amplitude and time as confirmed by the reduction of sp2 domain (La) and flake size. This also validates the formation of edge-type defect in graphene. Convincingly, lower amplitude and time (up to 60 min) produce better results for a low defect content and larger particle size as quantified by Raman analysis. 相似文献
5.
Cavitation in thin layer of liquid metal has potential applications in chemical reaction, soldering, extraction, and therapeutic equipment. In this work, the cavitation characteristics and acoustic pressure of a thin liquid Ga–In alloy were studied by high speed photography, numerical simulation, and bubble dynamics calculation. A self-made ultrasonic system with a TC4 sonotrode, was operated at a frequency of 20 kHz and a max output power of 1000 W during the cavitation recording experiment. The pressure field characteristic inside the thin liquid layer and its influence on the intensity, types, dimensions, and life cycles of cavitation bubbles and on the cavitation evolution process against experimental parameters were systematically studied. The results showed that acoustic pressure inside the thin liquid layer presented alternating positive and negative characteristics within 1 acoustic period (T). Cavitation bubbles nucleated and grew during the negative-pressure stage and shrank and collapsed during the positive-pressure stage. A high bubble growth speed of 16.8 m/s was obtained and evidenced by bubble dynamics calculation. The maximum absolute pressure was obtained at the bottom of the thin liquid layer and resulted in the strongest cavitation. Cavitation was divided into violent and weak stages. The violent cavitation stage lasted several hundreds of acoustic periods and had higher bubble intensity than the weak cavitation stage. Cavitation cloud preferentially appeared during the violent cavitation stage and had a life of several acoustic periods. Tiny cavitation bubbles with life cycles shorter than 1 T dominated the cavitation field. High cavitation intensities were observed at high ultrasonication power and when Q235B alloy was used because such conditions lead to high amplitudes on the substrate and further high acoustic pressure inside the liquid. 相似文献
6.
Ultrasound and plant extract are two green approaches that have been used to synthesize gold nanoparticles (AuNPs); however, how the combination of ultrasound and citrus peel extract (CPE) affects the structure characteristics and the bioactivity of AuNPs remains unknown. Here we investigated the effects of ultrasound conditions on the particle size, stability, yield, phenolic encapsulation efficacy, and the anti-inflammatory activity of AuNPs. The results showed that temperature was positively correlated to the particle size and the anti-inflammatory activity of synthesized AuNPs. Increasing the power intensity significantly decreased the particle size, while increased the change of total phenolic content (ΔTPC) in the reaction mixture. The increase of ΔTPC caused the enhanced anti-inflammatory activity of AuNPs. The AuNPs synthesized with or without ultrasound treatment were characterized using UV–Vis, DLS, SEM, TEM, EDS, XRD, and FT-IR. The result verified the formation of negatively charged, spherical, stable, and monodispersed AuNPs. AuNPs synthesized with ultrasound (AuNPs-U) has smaller particle size (13.65 nm vs 16.80 nm), greater yield and anti-inflammatory activity (IC50, 82.91 vs 157.71 μg/mL) than its non-ultrasound counterpart (AuNPs-NU). HPLC analysis showed that hesperidin was the key reductant for the synthesis of AuNPs. AuNPs-U also inhibited the mRNA and protein expression of iNOS and COX-2 in the LPS-induced Raw 264.7 cells. Our research elucidates the relationship between the reaction conditions and the structure characteristics and the anti-inflammatory activity of AuNPs synthesized using CPE with the help of ultrasound, thereafter, provides a feasible and economic way to synthesize AuNPs that can be used to ameliorate inflammation. 相似文献
7.
Cleaning of the flat sheet nanofiltration membranes, using backflushing, chemical cleaning, and ultrasonication operated individually as well as in combination with chemicals, has been studied in the present work. Identical hydrophilic polyamide membranes were fouled individually using an aqueous solution containing a single dye, an aqueous solution containing a mixture of dyes, and a synthetically prepared petroleum refinery effluent. Effect of different parameters such as the concentration of cleaning solution, contact time, frequency, and power of ultrasound on the efficacy of membrane cleaning has been studied. Optimal cleaning was achieved under sonication conditions of frequency of 24 kHz and power dissipation of 135 W. It was demonstrated that application of sonication under optimum conditions without chemical agents, gave about 85% water flux recovery. In the case of combined chemical and ultrasonic treatment, it was clearly observed that the use of chemical agent increased the efficacy of ultrasonic cleaning. The hybrid method recovered the initial water flux to almost 90% based on the use of 1.0 M aqueous NaOH and 4 min of sonication. Overall, the use of aqueous NaOH in combination with sonication showed a better efficiency for cleaning than the individual processes thus demonstrating a new avenue for membrane cleaning. 相似文献
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Phase-changeable contrast agents have been proposed as a next-generation ultrasound contrast agent over conventional microbubbles given its stability, longer circulation time and ability to extravasate. Safe vaporization of nanodroplets (NDs) plays an essential role in the practical translation of ND applications in industry and medical therapy. In particular, the exposure parameters for initializing phase change as well as the site of phase change are concerned to be controlled. Compared to the traditional optical vaporization or acoustic droplet vaporization, this study exhibited the potential of using simultaneous, single burst laser and ultrasound incidence as a means of activating phase change of NDs to generate cavitation nuclei with reduced fluence and sound pressure. A theoretical model considering the laser heating, vapor cavity nucleation and growth was established, where qualitative agreement with experiment findings were found in terms of the trend of combined exposure parameters in order to achieve the same level of vaporization outcome. The results indicate that using single burst laser pulse and 10-cycle ultrasound might be sufficient to lower the exposure levels under FDA limit for laser skin exposure and ultrasound imaging. The combination of laser and ultrasound also provides temporal and spatial control of ND vaporization and cavitation nucleation without altering the sound field, which is beneficial for further safe and effective applications of phase-changeable NDs in medical, environmental, food processing and other industrial areas. 相似文献
10.
Recently, emerging evidence has demonstrated that cavitation actually creates important bidirectional channels on biological barriers for both intratumoral drug delivery and extratumoral biomarker release. To promote the barrier-breaking effects of cavitation for both therapy and diagnosis, we first reviewed recent technical advances of ultrasound and its contrast agents (microbubbles, nanodroplets, and gas-stabilizing nanoparticles) and then reported the newly-revealed cavitation physical details. In particular, we summarized five types of cellular responses of cavitation in breaking the plasma membrane (membrane retraction, sonoporation, endocytosis/exocytosis, blebbing and apoptosis) and compared the vascular cavitation effects of three different types of ultrasound contrast agents in breaking the blood-tumor barrier and tumor microenvironment. Moreover, we highlighted the current achievements of the barrier-breaking effects of cavitation in mediating drug delivery and biomarker release. We emphasized that the precise induction of a specific cavitation effect for barrier-breaking was still challenged by the complex combination of multiple acoustic and non-acoustic cavitation parameters. Therefore, we provided the cutting-edge in-situ cavitation imaging and feedback control methods and suggested the development of an international cavitation quantification standard for the clinical guidance of cavitation-mediated barrier-breaking effects. 相似文献
11.
The present study treats the effects of mass transport, heat transfer and chemical reactions heat on the bubble dynamics by spanning a range of ambient bubble radii. The thermodynamic behavior of the acoustic bubble was shown for three wave frequencies, 355, 515 and 1000 kHz. The used acoustic amplitude ranges from 1 to 3 atm. It has been demonstrated that the ambient bubble radius, R0, of the maximal response (i.e., maximal bubble temperature and pressure, Tmax and Pmax) is shifted toward lower values if the acoustic amplitude (at fixed frequency) or the ultrasonic frequency (at fixed amplitude) are increased. The range of the ambient bubble radius narrows as the ultrasonic frequency increases. Heat exchange at the bubble interface was found to be the most important mechanism within the bubble internal energy balance for acoustic amplitudes lower than 2.5 and 3 atm for ultrasonic frequencies of 355 and 515 kHz, respectively. For acoustic amplitudes greater or equal to 2.5 and 3 atm, corresponding to 355 and 515 kHz, respectively, mass transport mechanism (i.e., evaporation and condensation of water vapor) becomes dominant compared to the other mechanisms. At 1000 kHz, the mechanism of heat transfer persists to be dominant for all the used acoustic amplitudes (from 1 to 3 atm). Practically, all the above observations were maintained for bubbles at and around the optimum bubble radius, whereas no significant impact of the three energetic mechanisms was observed for bubbles of too lower and too higher values of R0 (limits of the investigated ranges of R0). 相似文献
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A mild, efficient, facile and eco-friendly procedure for the synthesis of 2,4-diarylthiazoles from arylthioamides and α-bromoacetophenones in 1-n-butyl-3-methylimidazolium tetrafluoroborate as a “green” media under ultrasound irradiation at room temperature is described. It is interesting to mention that only one product was obtained when two different α-bromoacetophenones were reacted with 1,3-phenyl dithioamide as the substrate. Work-up is very simple and there is no need to purify the product. A recycling study confirmed that the ionic liquid can be reused multiple times without a significant loss in its activity. 相似文献
14.
基于差分吸收光谱(DOAS)技术,结合自主搭建的一套小型便携式DOAS实验系统,开展了对氯气的实验测量。在处理氯气的标准截面时,比较了两种不同的高通数字滤波方法：三角函数滤波和多项式拟合滤波。实验证明采用后一处理方法能够更加准确反演出氯气的浓度。模拟计算的结果显示,采用五阶多项式处理的结果的误差较小;在不同样品池内的测量结果显示,利用该方法测量氯气的线性度达到0.996 1;实际的一条谱的反演结果显示拟合谱与测量谱基本重合,且剩余噪声谱的峰峰值最大值<5‰;给出整个实验过程中可能的误差主要来源。综合以上的实验结果表明,利用DOAS技术采用多项式拟合处理的方法可以实现对于氯气的检测。 相似文献
15.
We investigate the current-induced heat generation in a quantum dot (QD) coupled to four spin chemical potentials, which originate from the magnetic pumping field applied on the QD. Both resonant and non-resonant electron tunneling process is analyzed. It is found that the heat generation characteristic is mainly determined by the two spin chemical potentials lying nearest to the dot level. In particular, when the difference of this two potentials is less than two phonon energy, the heat generation exhibits quantum properties, unique behavior to nanosystems and absent in macroscopic bulks. 相似文献
16.
《Current Applied Physics》2014,14(8):1045-1050
In this study, we tried to reduce the organic contamination of graphene. This organic contamination most likely occurs during the graphene transfer and lithography steps, which in turn degrades the quality of the graphene. Inorganic Au film was applied for Au-assisted transfer instead of the conventional thin poly(methyl methacrylate), and a new fabrication process using the Au-film for the transfer and masking layer was designed in order to minimize the contamination of graphene from organic residues. As a result, we demonstrated that the overall qualities of the transferred graphene film and graphene transistors have been highly improved. These improvements include an enhancement of mobility, and a decrease of defects, unintentional doping, contact resistance, and sheet resistance. 相似文献
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为了实现原料肉新鲜度参数的无损在线实时评估,基于双波段可见/近红外反射光谱（350~1 100和1 000~2 500 nm）技术建立了原料肉新鲜度主要指标的在线检测系统。研究设计了装置的光源单元、光谱采集单元、控制单元和驱动单元,优化设计了光源固定支架和安放角度,编写了相应的控制程序,开发了实验室用和便于在不同生产线应用的两套在线检测系统。首先,对试验参数（传送带速度和样品到透镜入光口距离）进行了优化研究,通过光谱相似度比较和显著性分析,确定传送带速度是275 mm·s-1、距离是12 cm时能够获得更加稳定的光谱信号。然后,基于该试验参数,分别在静止和在线条件下采集了贮藏时间为1~13 d共50个猪肉样本的反射光谱,并利用抛物线拟合法对双波段光谱进行融合,以获取整条覆盖可见及近红外区域的完整光谱。为了使两个波段范围内的光谱数据点权重相同,在整个波段范围内均匀分布,借助三次样条插值法将所有光谱数据点以2 nm为间隔进行重新排布。采用窗口移动多项式最小二乘拟合法对光谱作平滑处理,采用标准正态变量变换对每条光谱进行标准化预处理,分别建立了静止和在线条件下新鲜度主要表征指标-颜色（L*,a*和b*）、pH和挥发性盐基氮的预测模型,以此验证所搭建系统的可靠性。经过对比分析,发现在线条件下的建模结果不如静止状态下的建模结果,这可能与在线采集时光谱存在漂移现象有关。进一步尝试利用一阶导数处理来消除基线漂移强化谱带特征,并对一阶导数和标准化处理顺序对建模结果的影响进行了探讨。结果发现先经过一阶导数再经过标准化处理,能更好地消除外部干扰造成的影响,建模结果更佳。在该处理方式下,基于第一波段光谱建立了颜色参数（L*,a*,b*）的预测模型,基于双波段光谱建立了pH和挥发性盐基氮的在线检测模型,预测相关系数分别为0.955 3,0.924 7,0.955 1,0.961 5和0.966 8。最后,为了验证模型的适用性,基于开发的便于在不同生产线应用的在线检测系统,利用独立的20个样本对在线模型进行外部验证,对颜色参数（L*,a*,b*）,pH和挥发性盐基氮的预测相关系数分别为0.918 9,0.914 1,0.947 7,0.950 4和0.960 6。研究结果表明,该系统通过双波段光谱的实时采集和融合,可以获取更多反应样本内部信息的光学信号,具有更强的检测能力。结合设计的光路等其他硬件单元,可以同时获取样本表面更大区域的反射光谱信息,从而实现对原料肉新鲜度主要表征参数的无损、在线、实时评估。该系统便于组装和拆卸,可以适应不同企业生产线的实际需要,具有较强的实用价值和较好的市场前景。 相似文献
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快速准确识别不明危险液体在公共安全领域需求明显.拉曼光谱技术因具有快速、灵敏、可非接触式检测等优点,成为近年来此领域的研究热点.以沙林、梭曼、塔崩、维埃克斯、芥子气等化学毒剂,磷酸三甲酯、磷酸三乙酯、磷酸三丁酯、甲基膦酸二甲酯、甲基膦酸二异丙酯等化学毒剂模拟剂,亚磷酸二甲酯、亚磷酸三甲酯、亚磷酸三乙酯、甲基膦酰氯乙酯、... 相似文献
20.
Meat emulsions were prepared by replacing water with basic electrolyzed water (BEW) and reducing NaCl content by 0, 10, 20, 30, 40, and 50%. The emulsions were sonicated in an ultrasound bath (25 kHz, 175 W, normal mode) for 0, 10, and 20 min. The physicochemical (pH, redox potential, water activity, and color parameters) and technological (cooking yield, emulsion stability, and texture) characteristics were evaluated. The US operation time of 20 min improved the emulsion stability, cooking yield, and texture of the emulsions with 10% and 20% NaCl reduction. The BEW-treated emulsions exhibited good fat retention and moderate water retention capacity. The combination of US and BEW for 20 min provided good emulsion stability and cooking yield for the formulations with up to 30% NaCl reduction, which exhibited texture profile similar to the control (0% NaCl reduction). Therefore, it is possible to produce reduced-salt meat emulsions using the combination of US and BEW. 相似文献