771 research outputs found
Ultra-fast escape of a deformable jet-propelled body
No full textIn this work a cephalopod-like deformable body that fills an internal cavity with fluid and expels it to propel an escape manoeuvre, while undergoing a drastic external shape change through shrinking, is shown to employ viscous as well as mainly inviscid hydrodynamic mechanisms to power an impressively fast start. First, we show that recovery of added-mass energy enables a shrinking rocket in a dense inviscid flow to achieve greater escape speed than an identical rocket in a vacuum. Next, we extend the shrinking body results of Weymouth & Triantafyllou (J. Fluid Mech., vol. 702, 2012, pp. 470–487) to three-dimensional bodies and show that three hydrodynamic mechanisms must be combined to achieve rapid escape performance in a viscous fluid: added-mass energy recovery; flow separation elimination; and an optimized energy storage and recovery. In particular, we show that the mechanism of separation elimination achieved through rapid body shrinking, coordinated with the mechanism of recovering the initially imparted added-mass energy, is critical to achieving a high escape speed. Hence a flexible, collapsing body can be vastly superior to a rigid-shell jet-propelled body
Vortex-induced vibrations of a long flexible cylinder in shear flow
No full textWe investigate the in-line and cross-flow vortex-induced vibrations of a long cylindrical tensioned beam, with length to diameter ratio L/D = 200, placed within a linearly sheared oncoming flow, using three-dimensional direct numerical simulation. The study is conducted at three Reynolds numbers, from 110 to 1100 based on maximum velocity, so as to include the transition to turbulence in the wake. The selected tension and bending stiffness lead to high-wavenumber vibrations, similar to those encountered in long ocean structures. The resulting vortex-induced vibrations consist of a mixture of standing and travelling wave patterns in both the in-line and cross-flow directions; the travelling wave component is preferentially oriented from high to low velocity regions. The in-line and cross-flow vibrations have a frequency ratio approximately equal to 2. Lock-in, the phenomenon of self-excited vibrations accompanied by synchronization between the vortex shedding and cross-flow vibration frequencies, occurs in the high-velocity region, extending across 30% or more of the beam length. The occurrence of lock-in disrupts the spanwise regularity of the cellular patterns observed in the wake of stationary cylinders in shear flow. The wake exhibits an oblique vortex shedding pattern, inclined in the direction of the travelling wave component of the cylinder vibrations. Vortex splittings occur between spanwise cells of constant vortex shedding frequency. The flow excites the cylinder under the lock-in condition with a preferential in-line versus cross-flow motion phase difference corresponding to counter-clockwise, figure-eight orbits; but it damps cylinder vibrations in the non-lock-in region. Both mono-frequency and multi-frequency responses may be excited. In the case of multi-frequency response and within the lock-in region, the wake can lock in to different frequencies at various spanwise locations; however, lock-in is a locally mono-frequency event, and hence the flow supplies energy to the structure mainly at the local lock-in frequency.United States. Office of Naval Research (Grant N00014-07-1-0135)United States. Office of Naval Research (Grant N00014-07-1-0446)BP (Firm) (MIT Major Projects Research Program
Erratum: Corrigendum to “Esophageal remnant cancer 35 years after acidic caustic injury: A case report” (International Journal of Surgery Case Reports (2016) 25 (215–217) (S2210261216302358) (10.1016/j.ijscr.2016.06.051))
No full textThe authors regret to change the first name of the second author; more specifically we would like to change the first name “Stamatina” to “Tania”—the family name (“Triantafyllou”) remains as it is. On behalf of all the authors, I assure that we are in agreement with this change. The authors would like to apologise for any inconvenience caused. © 2016 The Author(s
Meta-analysis indicates that add-on devices and new endoscopes reduce colonoscopy adenoma miss rate
No full textMolecular events in relapsed oral squamous cell carcinoma: Recurrence vs secondary primary tumor
No full textSao Paulo Research Foundation (FAPESP) [2011/13315-4, 2013/09142-2]Gleber-Netto, F.O., Braakhuis, B.J.M., Triantafyllou, A., Takes, R.P., Kelner, N., Rodrigo, J.P., Strojan, P., Poorten, V.V., Rapidis, A.D., Rinaldo, A., Brakenhoff, R.H., Ferlito, A., Kowalski, L.P
Neutrophil to Lymphocyte Ratio in Oropharyngeal Squamous Cell Carcinoma: A Systematic Review and Meta-Analysis
No full textThis study was supported by grants from the Plan Nacional de I+D+I 2013–2016 (ISCIII (PI19/00560 to J.P.R.), CIBERONC (CB16/12/00390 to J.P.R.), Ayudas a Grupos PCTI Principado de Asturias (IDI/2021/000079 to J.P.R.), and the FEDER Funding Program from the European Union.Rodrigo J.P., Sánchez-Canteli M., Triantafyllou A., de Bree R., Mäkitie A.A., Franchi A., Hellquist H., Saba N.F., Stenman G., Takes R.P., Valero C., Zidar N., Ferlito A
Compared Abilities of Endoscopic Techniques to Increase Colon Adenoma Detection Rates: A Network Meta-analysis
No full textSignature Based Analysis of <i>m</I>-consecutive-<i>k< <i>f</I> Systems With Exchangeable Components
No full textTriantafyllou, Ioannis S./0000-0002-7512-5217; Eryilmaz, Serkan/0000-0002-2108-1781; Koutras, Markos/0000-0001-5160-2405In this article, we study reliability properties of m-consecutive-k-out-of-n: F systems with exchangeable components. We deduce exact formulae and recurrence relations for the signature of the system. Closed form expressions for the survival function and the lifetime distribution as a mixture of the distribution of order statistics are established as well. These representations facilitate the computation of several reliability characteristics of the system for a given exchangeable joint distribution or survival function. Finally, we provide signature-based stochastic ordering results for the system's lifetime and investigate the IFR preservation property under the formulation of m-consecutive-k-out-of-n: F systems. (C) 2011 Wiley Periodicals, Inc. Naval Research Logistics 58: 344-354, 201
Comparative accuracy of needle sizes and designs for EUS tissue sampling of solid pancreatic masses: a network meta-analysis
No full textBackground and Aims: Variable diagnostic performance of sampling techniques during EUS-guided tissue
acquisition of solid pancreatic masses based on needle type (FNA versus fine-needle biopsy [FNB]) and gauge
(19-gauge vs 22-gauge vs 25-gauge) has been reported. We performed a systematic review with network metaanalysis
to compare the diagnostic accuracy of EUS-guided techniques for sampling solid pancreatic masses.
Methods: Through a systematic literature review to November 2018, we identified 27 randomized controlled trials
(2711 patients) involving adults undergoing EUS-guided sampling of solid pancreatic masses that evaluated the
diagnostic performance of FNA and FNB needles based on needle gauge. The primary outcome was diagnostic
accuracy. Secondary outcomes were sample adequacy, histologic core procurement rate, and number of needle
passes. We performed pairwise and network meta-analyses and appraised the quality of evidence using GRADE
(Grading of Recommendations Assessment, Development and Evaluation) methodology.
Results: In the network meta-analysis, no specific EUS-guided tissue sampling technique was superior, based on
needle type (FNA vs FNB) or gauge (19-gauge vs 22-gauge vs 25-gauge) (low-quality evidence). Specifically, there
was no difference between 25-gauge FNA versus 22-gauge FNA (relative risk [RR], 1.03; 95% confidence interval
[CI], 0.91-1.17) and 22-gauge FNB versus 22-gauge FNA (RR, 1.03; 95% CI, 0.89-1.18) needles for diagnostic
accuracy, sample adequacy, and histologic core procurement. Findings were confirmed in sensitivity analysis
restricted to studies with no rapid on-site cytologic evaluation and no use of the fanning technique.
Conclusion: In a network meta-analysis, no specific EUS-guided tissue sampling technique was superior with
regard to diagnostic accuracy, sample adequacy, or histologic procurement rate for solid pancreatic masses,
with low confidence in estimate
Nonlinear longitudinal/transversal modal interactions in highly extensible suspended cables
No full textRecent research literature mostly deals with nonlinear resonant dynamics of low-extensible cables involving transversal modes. Herein, we aim to investigate geometrically nonlinear longitudinal/transversal modal interactions in highly extensible suspended cables, whose material properties are assumed to be linearly elastic. Depending on cable elasto-geometric properties, the spectrum of low-order planar frequencies manifests primary and secondary frequency crossover phenomena of transversal/transversal and longitudinal/transversal modes, respectively. By focusing on 1:1 internal resonances, nonlinear equations of finite-amplitude, harmonically forced and damped, cable motion are considered, fully accounting for overall inertia and displacement coupling effects. Meaningful quadratic nonlinear contributions of non-resonant, higher-order, longitudinal modes are highlighted via a multimode-based, second-order multiple scales solution. Overall coupled/uncoupled dynamic responses, bifurcations, stability and space-time-varying displacements due to longitudinal/transversal (vs. transversal/transversal) modal interactions at secondary (vs. primary) crossovers are analytically and numerically evaluated, along with the resonant longitudinal mode-induced dynamic forces
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