Effect of central and non-central frequency components on the quality of damage imaging

Accurate image reconstruction of damage through Lamb wave diffraction tomography (LWDT) requires substantial information of scatter field. This can be achieved using transducer network to collect the scatter field data. However, this requires a large number of transducers that creates logistical constraints for the practical applications of the technique. Various methods have been developed to improve the practicability of LWDT. One of the main approaches is to employ data at multiple frequencies within the bandwidth of the excitation signal. The objective of this study is to investigate the performance of using the data at non-central frequencies to reconstruct the damage image using LWDT. This provides an understanding on the influence of data at each individual frequency in the damage image reconstruction.In this paper, a series of numerical case studies with consideration of different damage sizes and shapes are carried out. Different non-central frequencies data is used to reconstruct the damage image. The results show that using the data at different non-central frequencies leads to different qualities of the reconstructed damage images. The quality of these reconstructed damage images are then compared to investigate the information contained of the data at each individual frequency. The study shows that the non-central frequencies data can provide additional information in the damage image reconstruction. Overall, the results of this study provide insights into the influences of the data at different frequencies, which is essential to advance the developments of the LWDT.Gnana Teja Pudipeddi, Ching-Tai Ng, Andrei Kotouso

A Short History of the Drug Receptor Concept

Humans have long used plant and animal extracts for their medicinal properties but until the end of the 19th century their actions were often explained in a speculative manner. The systematic study of drugs did not begin until the 1860s, and the concept of receptors as the target of their effects in the body only emerged at the end of the 19th century from the brilliant and independent studies of John Newport Langley (1852-1925) and Paul Ehrlich (1854-1915). This book address the people and the key discoveries that led to the development of the receptor concept and its impact on 20th-century medicine: A.J Clark in the 1930s, and later E.J Ariens and R.P Stephenson in the 1950s provided the quantitative basis of drug receptor occupancy theory. R.P Ahlquist's investigations gave rise to the proposal of receptor subtypes in 1948 and facilitated Sir James Black (and subsequently others) to apply the receptor concept to clinical therapy (beta blockers) in the mid 1960s. By the early 1980s, the first (acetylcholine) receptor had been isolated and cloned. Today, we recognize a large and diverse number of physiological receptors which can be delineated into 'receptor super-families' on the basis of their pharmacology and molecular properties. These receptors are now the focus of a multi-national, multi-billion dollar pharmaceutical industry. This book reveals that these successes were by no means foreseeable, since chance, coincidence, competition among scientists, and other factors played important roles in the history of the receptor concept

Uptake and depuration of organic contaminants by blue mussels (Mytilus edulis) exposed to environmentally contaminated sediment

Experiments were designed to expose blue mussels (Mytilus edulis) to contaminated sediment collected from Narragansett Bay, Rhode Island, USA in 1982. Measurements were taken to allow comparisons of the uptake and depuration of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). In addition, concentration factors in the mussels were calculated separately against the dissolved and particulate phase concentrations and the results from the exposure and control systems were compared. Both PAHs and PCBs were rapidly accumulated by the mussels exposed to the contaminated sediment. After the mussels were transferred to control seawater, individual PAHs were depurated with half-lives ranging from 12 to 30 d. Individual PCBs showed depuration half-lives which ranged from 16 to 46 d. Concentration factors in the mussels calculated against the particulate phase concentrations were very different in the exposure and control systems. Concentration factors calculated using only the dissolved phase concentrations (bioconcentration factors) showed excellent agreement in the two systems, possibly an indication that the dissolved phase was the direct source of the contaminants accumulated by the mussels. The bioconcentration factors for PCBs were higher than those of PAHs when compounds with similar n-octanol/water partition coefficients were compared. © 1986 Springer-Verlag