Estimating Phase Velocity and Attenuation of Guided Waves in Acoustic Logging Data

Phase velocity and attenuation of guided waves have been estimated from multireceiver, full waveform, acoustic logging data using the extended Prony's method. Since a formation affects velocity and attenuation, estimating these quantities is important in evaluating the formation properties. The estimation is performed using an array processing technique which requires two steps: (1) the traces for all receivers are transformed into the frequency domain, and (2) for each frequency the extended Prony's method is used to determine the presence of a guided wave propagating past the array of receivers. The guided wave properties estimated by the Prony's method include amplitude, attenuation, and phase change which is related to phase velocity. An important assumption in this array processing technique is that the formation, borehole fluid, and tool are homogeneous along the receiving array. For synthetic data, the phase velocities and attenuation of the tube wave and two modes of the pseudo-Rayleigh wave are accurately estimated over many frequencies, with the exception that the low amplitude of the second mode causes its attenuation estimate to be somewhat less accurate. For laboratory data, very good estimates of the phase velocities of the tube wave and three modes of the pseudo-Rayleigh wave are obtained. Since the materials used in the laboratory experiment had very large quality factors, the attenuation could not be estimated. For field data, the dispersion of the tube wave and the velocity of the pseudo-Rayleigh wave at its cutoff are very close to those predicted by another, independent method. Accurate attenuation estimates could not be made because the data are noisy and consist of only eight traces.Massachusetts Institute of Technology. Full Waveform Acoustic Logging Consortiu

Spectrums of investment in Doctor Who fandom

Drawing upon a significant weight of empirical data, collected in the field, this thesis proposes a set of four spectrums of investment engaged in by cult media fans: the spectrum of financial investment; the spectrum of what is here termed 'participatory investment'; the spectrum of investment in the idea of textual authenticity; and the spectrum of multiple investments. The spectrum model allows the individual members of the research sample to be located within specific regions of each spectrum and correlations to be drawn between the distinct spectrums, in order for any patterns which emerge to be examined. The thesis also reviews a number of relevant theoretical concerns such as fan studies, ethnography and social psychology.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Oral iron exacerbates colitis and influences the intestinal microbiome

Inflammatory bowel disease (IBD) is associated with anaemia and oral iron replacement to correct this can be problematic, intensifying inflammation and tissue damage. The intestinal microbiota also plays a key role in the pathogenesis of IBD, and iron supplementation likely influences gut bacterial diversity in patients with IBD. Here, we assessed the impact of dietary iron, using chow diets containing either 100, 200 or 400 ppm, fed ad libitum to adult female C57BL/6 mice in the presence or absence of colitis induced using dextran sulfate sodium (DSS), on (i) clinical and histological severity of acute DSS-induced colitis, and (ii) faecal microbial diversity, as assessed by sequencing the V4 region of 16S rRNA. Increasing or decreasing dietary iron concentration from the standard 200 ppm exacerbated both clinical and histological severity of DSS-induced colitis. DSS-treated mice provided only half the standard levels of iron ad libitum (i.e. chow containing 100 ppm iron) lost more body weight than those receiving double the amount of standard iron (i.e. 400 ppm); p<0.01. Faecal calprotectin levels were significantly increased in the presence of colitis in those consuming 100 ppm iron at day 8 (5.94-fold) versus day-10 group (4.14-fold) (p<0.05), and for the 400 ppm day-8 group (8.17-fold) versus day-10 group (4.44-fold) (p<0.001). In the presence of colitis, dietary iron at 400 ppm resulted in a significant reduction in faecal abundance of Firmicutes and Bacteroidetes, and increase of Proteobacteria, changes which were not observed with lower dietary intake of iron at 100 ppm. Overall, altering dietary iron intake exacerbated DSS-induced colitis; increasing the iron content of the diet also led to changes in intestinal bacteria diversity and composition after colitis was induced with DSS

Comparison of Bacterial Diversity within the Coral Reef Sponge, Axinella corrugata, and the Encrusting Coral Erythropodium caribaeorum

We compared the Caribbean reef sponge, Axinella corrugata, with the Caribbean reef coral, Erythropodium caribaeorum for differences in their resident microbial communities. This cursory survey of bacterial diversity applied 16S rRNA gene sequences. Over 100 culture-independent sequences were generated from five different Axinella 16S rRNA libraries, and compared with 69 cultured isolates. The cultureindependent 16S rDNA clones displayed a higher diversity of Proteobacteria, including “uncultured” or “unknown” representatives from the Deltaproteobacteria. Arcobacterium, and Cyanobacteria were also found. We have also confirmed that Axinella sponges appeared to host specific microbial symbionts, similar to the previously identified clones termed “OSO” environmental samples. In contrast, seawater samples near Axinella were dominated by Pseudoalteromonas. Adjacent sediment samples yielded clones of Planctomycetacea, Proteobacteria, sulfate-reducing Desulfovibrio spp, and other Deltaproteobacteria. Anaerobe-like 16S rRNA sequences were detected after the oxygen supply to one Axinella sample was deliberately curtailed to assess temporal changes in the microbial community. E. caribaeorum yielded more Betaproteobacteria relative to Axinella 16S libraries, and also included the Gammaproteobacteria genus Spongiobacter. However, Axinella-derived microbes appeared phylogenetically deeper with greater sequence divergences than the coral. Overall this study indicated that marine microbial community diversity can be linked to specific source hosts and habitats

National observational study to evaluate the "cleanyourhands" campaign (NOSEC): a questionnaire based study of national implementation

INTRODUCTION: The number of national hand-hygiene campaigns has increased recently, following the World Health Organisation's (WHO) "Save Lives: clean your hands" initiative (2009), which offers hospitals a multi-component hand-hygiene intervention. The number of campaigns to be evaluated remains small. Most evaluations focus on consumption of alcohol hand rub (AHR). We are not aware of any evaluation reporting implementation of all campaign components. In a previously published report, we evaluated the effects of the English and Welsh cleanyourhands campaign (2004-8) on procurement of AHR and soap, and on selected healthcare associated infections. We now report on the implementation of each individual campaign component: provision of bedside AHR, ward posters, patient empowerment materials, audit and feedback, and guidance to secure institutional engagement. METHOD: SETTING: all 189 acute National Health Service (NHS) hospitals in England and Wales (December 2005-June 2008). Six postal questionnaires (five voluntary, one mandatory) were distributed to infection control teams six-monthly from 6 to 36 months post roll-out. Selection and attrition bias were measured. RESULTS: Response rates fell from 134 (71 %) at 6 months to 82 (44 %) at 30 months, rising to 167 (90 %) for the final mandatory one (36 months). There was no evidence of attrition or selection bias. Hospitals reported widespread early implementation of bedside AHR and posters and a gradual rise in audit. At 36 months, 90 % of respondents reported the campaign to be a top hospital priority, with implementation of AHR, posters and audit reported by 96 %, 97 % and 91 % respectively. Patient empowerment was less successful. CONCLUSIONS: The study suggests that all campaign components, apart from patient empowerment, were widely implemented and sustained. It supports previous work suggesting that adequate piloting, strong governmental support, refreshment of campaigns, and sufficient time to engage institutions help secure sustained implementation of a campaign's key components. The results should encourage countries wishing to launch coordinated national campaigns for hospitals to participate in the WHO's "Save Lives" initiative, which offers hospitals a similar multi-component intervention

Emergence of dissipative structures in current-carrying superconducting wires

We discuss the emergence of a spontaneous temperature and critical current spatial modulation in current-carrying high temperature superconducting wire. The modulation of the critical current along the wire on a scale of 3 - 10 mm forces a fraction of the transport current to crisscross the resistive interface between the superconducting film and normal metal stabilizer attached to it. This generates additional heat that allows such a structure to be self sustainable. Stability and the conditions for experimental observation of this phenomenon are also discussed.Comment: To be published in Phys. Rev. E (in section Chaos and Pattern Formation