Leak detection using cepstrum of cross-correlation of transient pressure wave signals

A new leak detection method is proposed here which is based on the cepstrum of the cross-correlation of the pressure signals from two transducers. Computational simulations of leaks with different properties, size, position and shape, in a straight pipe and a T-Junction network were studied. The proposed method was successful in estimating leakages and the pipeline features with a high precision. For the results with a straight pipe, this method is considerably more accurate than using the cross-correlation leak detection method or the cepstrum method alone. However, the results obtained by cepstrum and cepstrum of cross-correlation for the T-Junction case were quite accurate, while cepstrum alone showed a slightly better precision

Spectroscopy Unveils the Complex Nature of Terzan 5

We present the chemical abundance analysis of 33 red giant stars belonging to the complex stellar system Terzan 5. We confirm the discovery of two stellar populations (Ferraro et al. 2009, Nature, 462,483) with distinct iron abundances: a relatively metal-poor component with [Fe/H]=-0.25 +/- 0.07 r.m.s., and another component with [Fe/H]=+0.27 +/- 0.04 r.m.s., exceeding in metallicity any known Galactic globular cluster. The two populations also show different [alpha/Fe] abundance ratios. The metal-poor component has an average [alpha/Fe]=+0.34 +/- 0.06 r.m.s., consistent with the canonical scenario for rapid enrichment by core collapse supernovae (SNe). The metal-rich component has [alpha/Fe]=+0.03 +/-i 0.04 r.m.s., suggesting that the gas from which it formed was polluted by both type II and type Ia SNe on a longer timescale. Neither of the two populations shows evidence of the [Al/Fe] over [O/Fe] anti-correlation, that is typically observed in Galactic globular clusters. Because these chemical abundance patterns are unique, we propose that Terzan 5 is not a true globular cluster, but a stellar system with a much more complex history of star formation and chemical enrichment

The dynamics of the outer parts of omega Centauri

The multi-object fibre-fed spectrograph AAOmega at the Anglo-Australian Telescope has been used to establish and measure accurate (<1 kms-1) radial velocities for a new sample of members in the outer parts of the stellar system omega Centauri. The new sample more than doubles the number of known members with precise velocities that lie between 25' and 45' from the cluster center. Combining this sample with earlier work confirms that the line-of-sight velocity dispersion of omega Cen remains approximately constant at ~6.5 kms-1 in the outer parts of the cluster, which contain only a small fraction of the total cluster stellar mass. It is argued that the approximately constant velocity dispersion in the outer regions is most likely a consequence of external influences, such as the tidal shock heating that occurs each time omega Cen crosses the Galactic plane. There is therefore no requirement to invoke dark matter or non-standard gravitational theories.Comment: Accepted for publication in the Astrophysical Journal. 29 pages, 10 figure

Cost-effectiveness analysis of 3-D computerized tomography colonography versus optical colonoscopy for imaging symptomatic gastroenterology patients.

BACKGROUND: When symptomatic gastroenterology patients have an indication for colonic imaging, clinicians have a choice between optical colonoscopy (OC) and computerized tomography colonography with three-dimensional reconstruction (3-D CTC). 3-D CTC provides a minimally invasive and rapid evaluation of the entire colon, and it can be an efficient modality for diagnosing symptoms. It allows for a more targeted use of OC, which is associated with a higher risk of major adverse events and higher procedural costs. A case can be made for 3-D CTC as a primary test for colonic imaging followed if necessary by targeted therapeutic OC; however, the relative long-term costs and benefits of introducing 3-D CTC as a first-line investigation are unknown. AIM: The aim of this study was to assess the cost effectiveness of 3-D CTC versus OC for colonic imaging of symptomatic gastroenterology patients in the UK NHS. METHODS: We used a Markov model to follow a cohort of 100,000 symptomatic gastroenterology patients, aged 50 years or older, and estimate the expected lifetime outcomes, life years (LYs) and quality-adjusted life years (QALYs), and costs (£, 2010-2011) associated with 3-D CTC and OC. Sensitivity analyses were performed to assess the robustness of the base-case cost-effectiveness results to variation in input parameters and methodological assumptions. RESULTS: 3D-CTC provided a similar number of LYs (7.737 vs 7.739) and QALYs (7.013 vs 7.018) per individual compared with OC, and it was associated with substantially lower mean costs per patient (£467 vs £583), leading to a positive incremental net benefit. After accounting for the overall uncertainty, the probability of 3-D CTC being cost effective was around 60 %, at typical willingness-to-pay values of £20,000-£30,000 per QALY gained. CONCLUSION: 3-D CTC is a cost-saving and cost-effective option for colonic imaging of symptomatic gastroenterology patients compared with OC

Formation of Multiple Populations in Globular Clusters: Another Possible Scenario

While chemical composition spreads are now believed to be a universal characteristic of globular clusters (GCs), not all of them present multiple populations in their color-magnitude diagrams (CMDs). Here we present a new scenario for the formation of GCs, in an attempt to qualitatively explain this otherwise intriguing observational framework. Our scenario divides GCs into three groups, depending on the initial mass (M_I) of the progenitor structure (PS), as follows. i) Massive PSs can retain the gas ejected by massive stars, including the ejecta of core-collapse SNe. ii) Intermediate-mass PSs can retain at least a fraction of the fast winds of massive stars, but none of the core-collapse SNe ejecta. iii) Low-mass PSs can only retain the slow winds of intermediate-mass stars. Members of the first group would include omega Centauri (NGC 5139), M54 (NGC 6715), M22 (NGC 6656), and Terzan 5, whereas NGC 2808 (and possibly NGC 2419) would be members of the second group. The remaining GCs which only present a spread in light elements, such as O and Na, would be members of the third group. According to our scenario, the different components in omega Cen should not display a sizeable spread in age. We argue that this is consistent with the available observations. We give other simple arguments in favor of our scenario, which can be described in terms of two main analytical relations: i) Between the actual observed ratio between first and second generation stars (R_SG^FG) and the fraction of first generation stars that have been lost by the GC (S_L); and ii) Between S_L and M_I. We also suggest a series of future improvements and empirical tests that may help decide whether the proposed scenario properly describes the chemical evolution of GCs.Comment: Accepted for publication in Astronomy and Astrophysic

Distributional reaction time properties in the Eriksen task: marked differences or hidden similarities with the Simon task?

In conflict tasks, the irrelevant stimulus attribute needs to be suppressed for the correct response to be produced. In the Simon task, earlier researchers have proposed that this suppression is the reason that, after an initial increase, the interference effect decreases for longer RTs, as reflected by late, negative-going delta plots. This view has been challenged by observations of positive-going delta plots, even for long RTs, in other conflict tasks, despite a similar necessity for suppression. For late negative-going delta plots to be interpreted as reflecting suppression, a necessary, although maybe not sufficient, condition is that similar patterns should be observed for other conflict tasks. We reasoned that a similar suppression could be present, but hidden, in the Eriksen flanker task. By recording and analyzing electromyograms of the muscles involved in response execution, we could compute delta plots separately for trials that elicited a subthreshold incorrect response activation (partial error). Late negative-going delta plots were observable on partial-error trials, although they were weaker than for the Simon task, reducing the impact of this inversion on the overall distribution. We further showed that this pattern is modulated by time pressure. Those results indicate that mechanisms leading to negative-going delta plots, similar to those observed in the Simon task, are also at play in the Eriksen task. The link between negative-going delta plots and executive online control is discussed

How Do Physical Therapists Treat People with Knee Osteoarthritis, and What Drives Their Clinical Decisions? A Population-Based Cross-Sectional Survey.

Purpose: It is unclear how physical therapists in Florida currently treat people with knee osteoarthritis and whether current best evidence is used in clinical decision making. Methods: We conducted a survey of physical therapists in Florida. We assessed the perceived effectiveness and actual use of physical therapy (PT) interventions and quantified the association between the actual use of interventions and different characteristics of physical therapists. Results: A total of 413 physical therapists completed the survey. Most respondents perceived therapeutic exercise (94%) and education (93%) as being effective or very effective. Interventions least perceived as effective or very effective were electrotherapy (28%), wedged insole (20%), and ultrasound (19%). Physical therapists who followed the principles of evidence-based practice were more likely to use therapeutic exercise (OR 3.89; 95% CI: 1.21, 12.54) and education (OR 3.63; 95% CI: 1.40, 9.43) and less likely to use ultrasound (OR 0.32; 95% CI: 0.16, 0.63) and electrotherapy (OR 0.32; 95% CI: 0.17, 0.58). Results also indicated that older physical therapists were more likely to use ultrasound (OR 3.57; 95% CI: 1.60, 7.96), electrotherapy (OR 2.53; 95% CI: 1.17, 5.47), kinesiology tape (OR 3.82; 95% CI: 1.59, 9.18), and ice (OR 1.95; 95% CI: 1.02, 3.73). Conclusions: In line with clinical guidelines, most physical therapists use therapeutic exercise and education to treat people with knee osteoarthritis. However, interventions that lack scientific support, such as electrotherapy and ultrasound, are still used. A modifiable therapist characteristic, adherence to evidence-based practice, is positively associated with the use of interventions supported by scientific evidence

Right subclavian double steal syndrome: a case report

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Horizontal DNA transfer mechanisms of bacteria as weapons of intragenomic conflict

Horizontal DNA transfer (HDT) is a pervasive mechanism of diversification in many microbial species, but its primary evolutionary role remains controversial. Much recent research has emphasised the adaptive benefit of acquiring novel DNA, but here we argue instead that intragenomic conflict provides a coherent framework for understanding the evolutionary origins of HDT. To test this hypothesis, we developed a mathematical model of a clonally descended bacterial population undergoing HDT through transmission of mobile genetic elements (MGEs) and genetic transformation. Including the known bias of transformation toward the acquisition of shorter alleles into the model suggested it could be an effective means of counteracting the spread of MGEs. Both constitutive and transient competence for transformation were found to provide an effective defence against parasitic MGEs; transient competence could also be effective at permitting the selective spread of MGEs conferring a benefit on their host bacterium. The coordination of transient competence with cell-cell killing, observed in multiple species, was found to result in synergistic blocking of MGE transmission through releasing genomic DNA for homologous recombination while simultaneously reducing horizontal MGE spread by lowering the local cell density. To evaluate the feasibility of the functions suggested by the modelling analysis, we analysed genomic data from longitudinal sampling of individuals carrying Streptococcus pneumoniae. This revealed the frequent within-host coexistence of clonally descended cells that differed in their MGE infection status, a necessary condition for the proposed mechanism to operate. Additionally, we found multiple examples of MGEs inhibiting transformation through integrative disruption of genes encoding the competence machinery across many species, providing evidence of an ongoing "arms race." Reduced rates of transformation have also been observed in cells infected by MGEs that reduce the concentration of extracellular DNA through secretion of DNases. Simulations predicted that either mechanism of limiting transformation would benefit individual MGEs, but also that this tactic's effectiveness was limited by competition with other MGEs coinfecting the same cell. A further observed behaviour we hypothesised to reduce elimination by transformation was MGE activation when cells become competent. Our model predicted that this response was effective at counteracting transformation independently of competing MGEs. Therefore, this framework is able to explain both common properties of MGEs, and the seemingly paradoxical bacterial behaviours of transformation and cell-cell killing within clonally related populations, as the consequences of intragenomic conflict between self-replicating chromosomes and parasitic MGEs. The antagonistic nature of the different mechanisms of HDT over short timescales means their contribution to bacterial evolution is likely to be substantially greater than previously appreciated

Role-play for medical students learning about communication: Guidelines for maximising benefits

BACKGROUND: Role-play is widely used as an educational method for learning about communication in medical education. Although educational theory provides a sound rationale for using this form of simulation, there is little published evidence for its effectiveness. Students' prior experiences of role-play may influence the way in which they engage in this method. This paper explores students' experiences with the aim of producing guidelines for maximising the benefits of role-play within this learning context. METHODS: First-year undergraduate medical students participated in a role-play session as part of their communication programme. Before and after the session, students completed questionnaires. In the pre-session questionnaire, students were asked about their experiences of role-play and asked to identify helpful and unhelpful elements. Immediately after the session, students answered similar questions in relation to the role-play activity they had just completed. Descriptive statistics were used to analyse quantitative data and qualitative data was thematically analysed. RESULTS: 284 students completed evaluation forms. Although 63 (22.2%) had prior unhelpful experiences, most students (n = 274; 96.5%) found this experience helpful. Summary findings were that students reported the key aspects of helpful role-play were opportunities for observation, rehearsal and discussion, realistic roles and alignment of roles with other aspects of the curriculum. Unhelpful aspects were those that evoked strong negative emotional responses and factors that contributed to a lack of realism. CONCLUSION: Role-play was valued by students in the acquisition of communication skills even though some had prior unhelpful experiences. Guidelines for effective role-play include adequate preparation, alignment of roles and tasks with level of practice, structured feedback guidelines and acknowledgment of the importance of social interactions for learning