ABSTRACT
Thin piezoelectric polymer films are used in increasingly more high frequency applications. However, they are not well characterized up to the gigahertz range. In this paper, polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) films are mechanically and electrically characterized using the electro-acoustic reflectometry (EAR) method from 20 MHz to 2 GHz. In addition to mechanical and electrical properties, nonuniform poling is detected in the tested PVDF-TrFE samples showing a larger piezoelectric constant in the middle of the film and thus generating even and odd resonance modes.
ABSTRACT
Monitoring of the coastline and coastal processes, in particular sediment movement, is vital to ensure that erosion response is appropriate given the dynamic nature of coastal systems. This should take place regularly over long periods and it is important that data are collected from submerged portions of the littoral zone, as well as the visible beach. This highlights two limitations in existing coastal monitoring techniques: 1. they require largely manual operation and 2. are limited to the visible beach, which results in an incomplete picture of what is happening in the coastal zone. Due to the current difficulties in gathering data beneath the sea surface, this paper reviews wireless sensor network (WSN) technology as a means to overcome these limitations. Analysis showed that WSNs are a promising technology for coastal monitoring, not only in terms of overcoming limitations, but also in terms of cost, safety, and the size of areas they are able to monitor. Previous work using WSNs in this environment is somewhat limited, especially as most current methods are largely limited to the visible beach, and do not consider submerged areas of the coastal zone. From consideration of the physical environment, geological and geographical processes, and informed by advances in technology, research gaps are identified, discussed and evaluated to provide strategies for implementation of WSNs to monitor sediment transport.
ABSTRACT
Although whole-organism HTS can give clear indications of in vivo activity, typically few clues are given as to the mechanism of action (MOA), and determining the MOA for large numbers of active compounds can be costly and complex-an alternative approach is required. This report demonstrates that it is possible to conduct relatively high throughput MOA characterization of HTS hits utilizing a single sample preparation and analytical method. By monitoring a wide range of endogenous cellular metabolites via (1)H nuclear magnetic resonance spectroscopy, the MOA of herbicides can be predicted using computational methods to compare the metabolite perturbation patterns. Herbicides that induce a characteristic pattern of metabolic perturbation in maize include inhibitors of acetolactate synthase, acetyl co-enzyme A carboxylase, protoporphyrinogen oxidase, 5-enolpyruvylshikimate-3-phosphate synthase, and phytoene desaturase. In soya, photosystem II inhibitors can also be detected, further demonstrating that this method is not limited to inhibitors of enzymes that directly act upon endogenous metabolites, or a single species. The methods, including data analysis, can be readily automated, enabling relatively high throughput MOA elucidation of whole-organism screen hits. Additionally, for compounds with a novel MOA, this approach may lead to MOA identification faster than traditional methods. It is envisaged that application of these data analysis methods to other data types-for example, transcription (mRNA) or translation (protein) profiles-is likely to permit higher throughput with smaller sample requirements, along with ability to discriminate MOAs that are not adequately discriminated based upon endogenous metabolite profiles.
