Dispersion behavior of torsional guided waves in a small diameter steel gas pipe

Condition monitoring of gas pipes has been an important issue for gas companies. Failure to accurately identify condition of gas pipes result in numerous problems. Also, producing a condition monitoring system for buried pipelines is challenging. Small pipes (with diameters less than 50 mm) are considered here as most of the literature focuses on larger pipes. Guided wave theory will be introduced alongside a numerical simulation of the relevant dispersion curves of the system. This paper investigates the feasibility of using torsional guided waves for inspecting defects in buried pipes with small diameters. The pipes are assumed to be lossless and hence the effect of attenuation is ignored in the calculations. Upon finding the theoretical guided wave characteristics, experiments were conducted to see if the aim could be achieved in a realistic scenario. A steel pipe with a diameter of 34 mm and wall thickness of 5.5 mm is considered. High reverberation levels at high frequency propagations due to mode conversion are studied. Having only a limited number of transducers could be a reason for high reverberation at high frequencies

Pirates of the Press: Case Studies in the Prehistory of Copyright

What do book pirates steal? Unlike buccaneers who plunder treasure from travelers, press-pirates seize reprinting rights from other publishers. In sixteenth-century England, Thomas Dekker first gave the name ‘pirates’ to those booksellers who navigated the dangerous waters of intellectual property by selling in-demand titles under false pretenses. Pirates operated even though London’s Worshipful Company of Stationers closely guarded booksellers’ privileges to print, known as ‘copies.’ Raids on the English book trade escalated until 1709, when a royal statute rescued writers and publishers by arguing that ‘copyright’ accrued always from a work to its author. The 1709 Copyright Act was a landmark in literary history and international property law, although it never entirely stopped piracy, especially across regional and national boundaries. The problem resurfaces today: as global media companies amass rights formerly held by authors, and book pirate bots trawl the digital seas. Co-Curated by UIUC Professor of English Lori Newcomb and RBML Curator of Rare Books Adam Doskey, the Fall exhibition in RBML explores the colorful lives of certain nefarious booksellers, the various means of identifying piracies, and the lasting impact of piracy on literary authorship and intellectual property law. Exhibits include examples of pirated works, books printed with false publisher information, and even a manuscript composed by a real, high-seas pirate that was itself pirated.Ope

Quantitative analysis of cryptic splicing associated with TDP-43 depletion

BACKGROUND: Reliable exon recognition is key to the splicing of pre-mRNAs into mature mRNAs. TDP-43 is an RNA-binding protein whose nuclear loss and cytoplasmic aggregation are a hallmark pathology in amyotrophic lateral sclerosis and frontotemporal dementia (ALS/FTD). TDP-43 depletion causes the aberrant inclusion of cryptic exons into a range of transcripts, but their extent, relevance to disease pathogenesis and whether they are caused by other RNA-binding proteins implicated in ALS/FTD are unknown. METHODS: We developed an analysis pipeline to discover and quantify cryptic exon inclusion and applied it to publicly available human and murine RNA-sequencing data. RESULTS: We detected widespread cryptic splicing in TDP-43 depletion datasets but almost none in another ALS/FTD-linked protein FUS. Sequence motif and iCLIP analysis of cryptic exons demonstrated that they are bound by TDP-43. Unlike the cryptic exons seen in hnRNP C depletion, those repressed by TDP-43 cannot be linked to transposable elements. Cryptic exons are poorly conserved and inclusion overwhelmingly leads to nonsense-mediated decay of the host transcript, with reduced transcript levels observed in differential expression analysis. RNA-protein interaction data on 73 different RNA-binding proteins showed that, in addition to TDP-43, 7 specifically bind TDP-43 linked cryptic exons. This suggests that TDP-43 competes with other splicing factors for binding to cryptic exons and can repress cryptic exon inclusion. CONCLUSIONS: Our quantitative analysis pipeline confirms the presence of cryptic exons during the depletion of TDP-43 but not FUS providing new insight into to RNA-processing dysfunction as a cause or consequence in ALS/FTD

NON-LINEAR PROPAGATION FOR MEDICAL IMAGING

Abstract The propagation of high amplitude ultrasonic fields, such as those generated by some medical ultrasound systems, is not adequately described by the linear wave equation. Instead it is necessary to consider non-linear propagation if the drive levels are high enough to make non-linear effects significant. As a result of non-linear propagation the transmitted waveforms distort as they propagate, resulting in the generation of harmonics of the initial frequency components transmitted by the transducer. In the nearfield of medical transducers diffraction and focusing effects associated with the source complicate this process. The basic physics of this non-linear propagation is reviewed and the complex characteristics of the finite amplitude fields generated by different sources are described. This is illustrated with both experimental results and numerical predictions obtained using a finite difference solution (the Bergen Code) to the Khokhlov-Zabolotskaya-Kuznetsov (or KZK) equation. The fields of both ideal sources and real medical systems are demonstrated. The use of harmonics to improve image quality is then considered, with the characteristics of the fields produced by harmonic imaging and pulse inversion systems being compared. The implications of non-linear propagation for medical ultrasound output regulation are also considered. Introduction The propagation of ultrasonic waves is often assumed to be a linear process. In this case the waves travel at a constant velocity (c 0 ) and so maintain their shape as they propagate. However, it is relatively easy to generate high enough pressures in ultrasonic fields for the effects of non-linear propagation to become significant, with the compressional phases of the wave travelling faster than the rarefactions. The resulting wave distortion (se

Analytical and numerical analyses of the micromechanics of soft fibrous connective tissues

State of the art research and treatment of biological tissues require accurate and efficient methods for describing their mechanical properties. Indeed, micromechanics motivated approaches provide a systematic method for elevating relevant data from the microscopic level to the macroscopic one. In this work the mechanical responses of hyperelastic tissues with one and two families of collagen fibers are analyzed by application of a new variational estimate accounting for their histology and the behaviors of their constituents. The resulting, close form expressions, are used to determine the overall response of the wall of a healthy human coronary artery. To demonstrate the accuracy of the proposed method these predictions are compared with corresponding 3-D finite element simulations of a periodic unit cell of the tissue with two families of fibers. Throughout, the analytical predictions for the highly nonlinear and anisotropic tissue are in agreement with the numerical simulations

Stability of multi-electron bubbles in liquid helium

The stability of multi-electron bubbles in liquid helium is investigated theoretically. We find that multi-electron bubbles are unstable against fission whenever the pressure is positive. It is shown that for moving bubbles the Bernoulli effect can result in a range of pressures over which the bubbles are stable.Comment: 7 pages, 5 figure

Density functional investigations of defect induced mid-gap states in graphane

We have carried out ab initio electronic structure calculations on graphane (hydrogenated graphene) with single and double vacancy defects. Our analysis of the density of states reveal that such vacancies induce the mid gap states and modify the band gap. The induced states are due to the unpaired electrons on carbon atoms. Interestingly the placement and the number of such states is found to be sensitive to the distance between the vacancies. Furthermore we also found that in most of the cases the vacancies induce a local magnetic moment.Comment: 15 page

Study of an advanced General Aviation Turbine Engine (GATE)

The best technology program for a small, economically viable gas turbine engine applicable to the general aviation helicopter and aircraft market for 1985-1990 was studied. Turboshaft and turboprop engines in the 112 to 746 kW (150 to 1000 hp) range and turbofan engines up to 6672 N (1500 lbf) thrust were considered. A good market for new turbine engines was predicted for 1988 providing aircraft are designed to capitalize on the advantages of the turbine engine. Parametric engine families were defined in terms of design and off-design performance, mass, and cost. These were evaluated in aircraft design missions selected to represent important market segments for fixed and rotary-wing applications. Payoff parameters influenced by engine cycle and configuration changes were aircraft gross mass, acquisition cost, total cost of ownership, and cash flow. Significant advantage over a current technology, small gas turbine engines was found especially in cost of ownership and fuel economy for airframes incorporating an air-cooled high-pressure ratio engine. A power class of 373 kW (500 hp) was recommended as the next frontier for technology advance where large improvements in fuel economy and engine mass appear possible through component research and development