Development of a computer model for an ultrasonic polymer film transducer system

A piezoelectric polymer film such as polyvinylidene fluoride (PVDF) offers the possibility of making cheap ultrasonic transducers which can be permanently bonded to structures for NDE applications. However, before this can be achieved it is necessary to have a full understanding of the behaviour of PVDF in the context of a transducer application. This paper describes the development of an interactive computer program to implement a one-dimensional model of a thin film transducer system mounted on a solid substrate. Starting from a typical transducer system mounted on a solid substrate. Starting from a typical tranducer equivalent circuit, this paper explains how that circuit can be expanded into a complete model representing a PVDF transducer with one or more backing layers bonded to an arbitrary solid substrate. The computer program uses this model to provide immediate predictions of electrical input impedence, acoustic response and pulse-echo response. A series of experiments has been performed using PVDF transducers bonded to a variety of materials in order to validate the model. This has enabled the degree of accuracy required for various parameters within the model, such as mechanical and dielectric loss values, to be assessed. Once validated, the model has been used as a tool to predict the effect of physical parameters, such as bond and electrode thickness, on the performance of a transducer.     

Sonification design for complex work domains: Dimensions and distractors.

Sonification—representing data in sound—is a potential method for supporting human operators who have to monitor dynamic processes. Previous research has investigated a limited number of sound dimensions and has not systematically investigated the impact of dimensional interactions on sonification effectiveness. In three experiments the authors investigated accuracy for identifying changes in six target auditory dimensions of a continuous pulse stream under three conditions: no distractor, one distractor, and five distractors. In Experiment 1 amplitude, frequency, harmonics, speed, tremolo (cycles per pulse), and width were tested. Accuracy and patterns of interaction between the dimensions were mapped. In Experiment 2 the same dimensions were tested but tremolo was operationalized as cycles per second (Hz). The patterns of interaction between the temporal dimensions differed from Experiment 1. In Experiment 3 the amplitude contour of the pulse stream was changed. The dimensions tested were amplitude, frequency, formants, speed, tremolo (cycles per period), and width. Results showed low accuracy for formants and many interactions, both positive and negative between the dimensions. The authors interpret the results in terms of theories of perceptual interference in auditory dimensions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recent advances in banana (musa spp.) biofortification to alleviate vitamin A deficiency

Abstract

Vitamin A deficiency (VAD) is one of the most prevalent micronutrient deficiencies that disproportionately affects low income populations in developing countries. Traditional breeding and modern biotechnology have significant potential to enhance micronutrient bioavailability in crops through biofortification. Bananas (Musa spp.) are economically important fruit crops grown throughout tropical and sub-tropical regions of the world where VAD is most prevalent. Some banana genotypes are rich in provitamin A carotenoids (pVACs), providing an opportunity to use bananas as a readily available vehicle for provitamin A delivery. This review summarizes the progress made in carotenoid research in bananas relative to banana diversity and the use of conventional breeding and transgenic approaches aimed at banana biofortification to address vitamin A deficiency. Existing reports on sampling strategies, pVAC retention and bioavailability are also evaluated as essential components for a successful banana biofortification effort. The wide variability of pVACs reported in banana cultivars coupled with recent advances in unraveling the diversity and genetic improvement of this globally important but often-neglected staple fruit crop underscores their importance in biofortification schemes.     

Comparative effect of direct-fed microbials on fecal shedding of Escherichia coli O157:H7 and Salmonella in naturally infected feedlot cattle

The effect of direct-fed microbials (DFM) on fecal shedding of Escherichia coli O157:H7 and Salmonella in naturally infected feedlot cattle was evaluated in a clinical trial involving 138 feedlot steers. Following standard laboratory methods, fecal samples collected from steers were evaluated for change in the detectable levels of E. coli O157:H7 and Salmonella shed in feces after DFM treatment. Sampling of steers was carried out every 3 weeks for 84 days. A significant reduction (32%) in fecal shedding of E. coli O157:H7 (P < 0.001), but not Salmonella (P = 0.24), was observed among the treatment steers compared with the control group during finishing. The probability of recovery of E. coli O157:H7 from the feces of treated and control steers was 34.0 and 66.0%, respectively. Steers placed on DFM supplement were almost three times less likely to shed E. coli O157:H7 (odds ratio, 0.36; 95% confidence interval, 0.25 to 0.53; P < 0.001) in their feces as opposed to their control counterparts. The probability of recovery of Salmonella from the feces of the control (14.0%) and the treated (11.3%) steers was similar. However, the DFM significantly reduced probability of new infections with Salmonella among DFM-treated cattle compared with controls (nontreated ones). It appears that DFM as applied in our study are capable of significantly reducing fecal shedding of E. coli O157:H7 in naturally infected cattle but not Salmonella. The factors responsible for the observed difference in the effects of DFM on E. coli O157:H7 and Salmonella warrants further investigation.     

Numerical Investigation of Creep Effects on FRP-Strengthened RC Beams

Numerical analysis using a finite-element model was performed to simulate and investigate the long-term behavior of two RC beams with similar steel reinforcement, cast from the same batch of concrete. One beam was a plain RC beam and the other beam was strengthened using carbon fiber-reinforced polymer (FRP) strips. The deflections of both beams have been monitored for 5 years after loading. The finite-element model included both creep of concrete and viscoelasticity of the epoxy adhesive at the concrete-carbon FRP (CFRP) interface. The results of the finite-element analysis are compared to experimental observations of the two beams. The finite-element analysis was found to be able to simulate the long-term behavior of the CFRP-strengthened beam and help us understand the complex changes in the stress state that occur over time.     

Behavioural Evidence and Chemical Identification of a Female Sex Pheromone in Anagrus atomus (Hymenoptera: Mymaridae)

Journal of Chemical Ecology - Anagrus atomus (L.) is an egg parasitoid involved in the biological control of Empoasca vitis (Göthe) in vineyards. Sex pheromones play a crucial role in mate...     

Fabrication of electrospun keratin nanofiber membranes for air and water treatment

Keratin proteins extracted from wool fibers by sulfitolysis were electrospun for the production of active nanofiber membranes (NFMs). The keratin NFMs were composited with nylon woven fabric for improving their mechanical properties as a filtration material. The prepared membranes were characterized in terms of morphology, pore size, contact angle, and performance of water and air permeability. Experimental data showed that most of investigated parameters were affected by the electrospinning time: that is, roughness rose by increasing the electrospinning time, while the narrowest pore size distribution was obtained at the longest electrospinning time (2 h). The pure water permeability (PWP) was greater for the produced NFMs than for the commercial microfiltration membranes and decreased by increasing the electrospinning time. At the longest electrospinning time, the produced NFMs showed a PWP of about 45.7 m³/m² h bar, which is a value greater than those obtained by conventional materials used in water filtration, including microfiltration membranes. According to the data of contact angle measurements, the high hydrophobicity of NFMs membranes could reinforce their stability in water. Other potential applications could be venting, adsorption of VOCs, and separation of oils from oil/water emulsions. POLYM. ENG. SCI., 59:1472–1478 2019. © 2019 Society of Plastics Engineers