Noninvasive liquid level sensing with laser generated ultrasonic waves.

This article proposes a noninvasive liquid level sensing technique using laser-generated ultrasound waves for nuclear power plant applications. Liquid level sensors play an important role of managing the coolant system safely and stably in the plant structure. Current sensing techniques are mostly intrusive, performing inside the fluidic structure, which is disadvantageous in terms of the regular maintenance of the plant system. Furthermore, typical intrusive sensors do not perform stably under varying environmental conditions such as temperature and radiation. In this study, sensing units are attached to the outer surface of a liquid vessel to capture guided ultrasound waves in a nonintrusive manner. The signal intensity of the guided wave dissipates when the signal interacts with the internal liquid media. The sensing mechanism is mathematically expressed as an index value to correlate the liquid level with the sensor signal. For the acoustic wave generation, laser-generated ultrasound was adopted instead of using typical contact type transducers. Following the simulation validation of the proposed concept, the performance of the developed sensor was confirmed through experimental results under elevated liquid temperature conditions. The nonlinear multivariable regression exhibited the best-fit to the datasets measured under the variable liquid level and temperature conditions.

Multifunctional ZnO/Nylon 6 nanofiber mats by an electrospinning-electrospraying hybrid process for use in protective applications.

ZnO/Nylon 6 nanofiber mats were prepared by an electrospinning-electrospraying hybrid process in which ZnO nanoparticles were dispersed on the surface of Nylon 6 nanofibers without becoming completely embedded. The prepared ZnO/Nylon 6 nanofiber mats were evaluated for their abilities to kill bacteria or inhibit their growth and to catalytically detoxify chemicals. Results showed that these ZnO/Nylon 6 nanofiber mats had excellent antibacterial efficiency (99.99%) against both the Gram-negative Escherichia coli and Gram-positive Bacillus cereus bacteria. In addition, they exhibited good detoxifying efficiency (95%) against paraoxon, a simulant of highly toxic chemicals. ZnO/Nylon 6 nanofiber mats were also deposited onto nylon/cotton woven fabrics and the nanofiber mats did not significantly affect the moisture vapor transmission rates and air permeability values of the fabrics. Therefore, ZnO/Nylon 6 nanofiber mats prepared by the electrospinning-electrospraying hybrid process are promising material candidates for protective applications.

Effects of temperature and molecular oxygen on the use of atmospheric pressure plasma as a novel method for insect control.

Helium atmospheric pressure plasma discharge (APPD) was previously shown to have insecticidal activity with a possible site of action on the insect nervous, neuromuscular system, or both. In the current study, methods to increase the insecticidal activity of plasma by using increased APPD temperature and the introduction of molecular oxygen were investigated for the first time. An increase in the helium plasma temperature from 37 to 50 degrees C increased the insecticidal activity of plasma for the control of the German cockroach, Blattella germanica (L.); western flower thrips, Frankliniella occidentalis (Pergande); and citrus mealybug, Planococcus citri (Risso). This increase in activity could not be explained by the increase in air temperature alone, and it suggests that the enhanced insecticidal activity resulted from increased ionization of the APPD and ion bombardment of the insect. Emission spectroscopy showed that the introduction of 0.5% oxygen into helium plasma produced ionic molecular oxygen at 559.7 and 597.3 nm. The introduction of oxygen to the APPD greatly increased the insecticidal activity of plasma for the citrus mealybug but not the German cockroach or western flower thrips. For the mealybug as an example, the mortality of a 60-s exposure of 37 degrees C helium plasma was 0% at 1 h after exposure and 100% under the same conditions after the introduction of oxygen. It seems that increases in temperature and the introduction of oxygen even at low levels can increase the insecticidal activity of plasma to varying degrees depending on the insect species. The symptomology of cockroach death for both hot plasma and plasma containing trace amounts of molecular oxygen continued to suggest that the site of action of APPD is the insect nervous system, neuromuscular system, or both.

Mode of action of a novel nonchemical method of insect control: atmospheric pressure plasma discharge.

Atmospheric pressure plasma discharge (APPD) has been applied to a number of industrial applications, including the bacterial sterilization of medical equipment of bacteria. APPD may also have applications in insect control. A positive correlation was found between exposure time to APPD and mortality of western flower thrips, Frankliniella occidentalis (Pergande); tobacco thrips, Frankliniella fusca (Hinds); Asian tiger mosquito, Aedes albopictus (Skuse); twospotted spider mite, Tetranychus urticae Koch; and German cockroach, Blattella germanica (L.), with the level of mortality also increasing with time after treatment. Cockroaches exposed to APPD for 60, 90, 120, and 180 s lost on average 7.5 +/- 0.8, 8.1 +/- 0.6, 8.7 +/- 0.4, and 10.1 +/- 1.1 (+/-1 SEM) mg of water weight, respectively, which was an increase over that of the controls. The metabolic rate of cockroaches exposed to plasma for 180 s increased from 0.79 +/- 0.03 to 1.07 +/- 0.04 ml of oxygen consumed mg-cockroach(-1) h(-1) at standard temperature and pressure. The level of cuticular hydrocarbons identified by electron impact gas chromatography-mass spectrometry were not significantly affected by plasma exposure in the green peach aphid, Myzus persicae (Sulzer), German cockroach, and citrus mealybug, Planococcus citri (Risso), except for a reduction in n-tritriacontane in the latter. However, changes in the behavior of cockroaches after plasma exposure, including the loss of photo-, vibro-, and thigmotropic responses, inability to right themselves, and hyperexcitatory symptoms, suggest that the site of action of APPD in insects is the nervous and/or neuromuscular system.