Validation of leading point concept in RANS simulations of highly turbulent lean syngas-air flames with well-pronounced diffusional-thermal effects

While significant increase in turbulent burning rate in lean premixed flames of hydrogen or hydrogen-containing fuel blends is well documented in various experiments and can be explained by highlighting local diffusional-thermal effects, capabilities of the vast majority of available models of turbulent combustion for predicting this increase have not yet been documented in numerical simulations. To fill this knowledge gap, a well-validated Turbulent Flame Closure (TFC) model of the influence of turbulence on premixed combustion, which, however, does not address the diffusional-thermal effects, is combined with the\ua0 leading point concept, which highlights strongly perturbed leading flame kernels whose local structure and burning rate are significantly affected by the diffusional-thermal effects. More specifically, within the framework of the leading point concept, local con sumption velocity is computed in extremely strained laminar flames by adopting detailed combustion chemistry and, subsequently, the computed velocity is used as an input parameter of the TFC model. The combined model is tested in RANS simulations of highly turbulent, lean syngas-air flames that were experimentally investigated at Georgia Tech. The tests are performed for four different values of the inlet rms turbulent velocities, different turbulence length scales, normal and elevated (up to 10 atm) pressures, various H2/CO ratios ranging from 30/70 to 90/10, and various equivalence ratios ranging from 0.40 to 0.80. All in all, the performed 33 tests indicate that the studied combination of the leading point concept and the TFC model can predict well-pronounced diffusional-thermal effects in lean highly turbulent syngas-air flames, with these results being obtained using the same value of a single constant of the combined model in all cases. In particular, the model well predicts a significant increase in the bulk turbulent consumption velocity when increasing the H2/CO ratio but retaining the same value of the laminar flame speed

Surgical management of laryngotracheal stenosis in adults

The purpose was to evaluate the outcome following the surgical management of a consecutive series of 26 adult patients with laryngotracheal stenosis of varied etiologies in a tertiary care center. Of the 83 patients who underwent surgery for laryngotracheal stenosis in the Department of Otorhinolaryngology and Head and Neck Surgery, University Hospital of Lausanne, Switzerland, between 1995 and 2003, 26 patients were adults (≥16years) and formed the group that was the focus of this study. The stenosis involved the trachea (20), subglottis (1), subglottis and trachea (2), glottis and subglottis (1) and glottis, subglottis and trachea (2). The etiology of the stenosis was post-intubation injury ( n =20), infiltration of the trachea by thyroid tumor ( n =3), seeding from a laryngeal tumor at the site of the tracheostoma ( n =1), idiopathic progressive subglottic stenosis ( n =1) and external laryngeal trauma ( n =1). Of the patients, 20 underwent tracheal resection and end-to-end anastomosis, and 5 patients had partial cricotracheal resection and thyrotracheal anastomosis. The length of resection varied from 1.5 to 6cm, with a median length of 3.4cm. Eighteen patients were extubated in the operating room, and six patients were extubated during a period of 12 to 72h after surgery. Two patients were decannulated at 12 and 18months, respectively. One patient, who developed anastomotic dehiscence 10days after surgery, underwent revision surgery with a good outcome. On long-term outcome assessment, 15 patients achieved excellent results, 7 patients had a good result and 4 patients died of causes unrelated to surgery (mean follow-up period of 3.6years). No patient showed evidence of restenosis. The excellent functional results of cricotracheal/tracheal resection and primary anastomosis in this series confirm the efficacy and reliability of this approach towards the management of laryngotracheal stenosis of varied etiologies. Similar to data in the literature, post-intubation injury was the leading cause of stenosis in our series. A resection length of up to 6cm with laryngeal release procedures (when necessary) was found to be technically feasibl

The role of the CO2 laser in the management of laryngotracheal stenosis: a survey of 100 cases

Over the last decade, improvement of CO2 lasers with the microspot and ultrapulse technologies has broadened the indications for endoscopic CO2-laser resection of benign laryngotracheal stenosis (LTS). This article reviews 100 patients treated solely by endoscopic means for a LTS. There were 47 grade III, 41 grade II and 12 grade I stenoses according to the Myer-Cotton classification. The postoperative results show that the improvement to a nearly normal (>80% luminal size) airway declines from 92% (11/12 patients) for grade I to 46% (19/41 patients) for grade II and 13% (6/47 patients) for grade III stenoses. When compared to open surgery for more severe grades of stenosis (31 grade IV, 66 grade III and 3 grade II stenoses), the results of the endoscopy group is much less favorable: 36% of patients in the endoscopy group versus 76% of patients in the open surgery group were rehabilitated to a normal respiration without exertional dyspnea and 38% versus 5% patients remained tracheotomy dependent. However, if strict selection and therapeutic criteria are respected, a significant number of grade I and II stenoses, and to a lesser degree of grade III stenoses, can be improved to a nearly normal airway by endoscopic means only. The endoscopic treatment is potentially less invasive and risky and only needs a short hospital stay. To try this as a first treatment modality in a selected group of patients is worthwhile, provided that this endoscopic treatment is not repeated a second time, if the stenosis recurs to its initial grade after a primary CO2-laser treatment. Some guidelines for safe endoscopic treatment modalities with of the CO2 laser, dilatation and/or stenting are propose

Meyer's surgical procedure for the treatment of lip carcinoma

Lip carcinomas are generally treated by surgery. A reconstruction is often required if the resected segment exceeds one-third of the lip. Meyer's plasty is an alternate way of reconstructing the lower or upper lip. The aim of this study is to describe the technique, its indications and results. A retrospective review of all patients who underwent a Meyer's plasty in our institution is presented. Twenty-four consecutive patients were treated in Lausanne for T1 and T2 lip carcinomas between 1983 and 2001. Primary surgery associated with Meyer's plasty was performed in all cases. Data were collected from the medical records, and eight patients were recalled for clinical evaluation. The oncological, functional and aesthetic results were analyzed. The 5-year local control was 100%. Three patients developed metachronous lymph node metastasis. No patient died from the disease. A hindering microstomy was found in three cases, and two patients suffered from temporary oral leakage. No speech difficulty was encountered. The aesthetics was described as satisfying or good in 87% of the patients. Meyer's plasty following lip surgery of the upper or lower lip allows an aesthetic and functional one-stage reconstruction without compromising the oncological outcom

A New Perspective on Listeria monocytogenes Evolution

Listeria monocytogenes is a model organism for cellular microbiology and host–pathogen interaction studies and an important food-borne pathogen widespread in the environment, thus representing an attractive model to study the evolution of virulence. The phylogenetic structure of L. monocytogenes was determined by sequencing internal portions of seven housekeeping genes (3,288 nucleotides) in 360 representative isolates. Fifty-eight of the 126 disclosed sequence types were grouped into seven well-demarcated clonal complexes (clones) that comprised almost 75% of clinical isolates. Each clone had a unique or dominant serotype (4b for clones 1, 2 and 4, 1/2b for clones 3 and 5, 1/2a for clone 7, and 1/2c for clone 9), with no association of clones with clinical forms of human listeriosis. Homologous recombination was extremely limited (r/m<1 for nucleotides), implying long-term genetic stability of multilocus genotypes over time. Bayesian analysis based on 438 SNPs recovered the three previously defined lineages, plus one unclassified isolate of mixed ancestry. The phylogenetic distribution of serotypes indicated that serotype 4b evolved once from 1/2b, the likely ancestral serotype of lineage I. Serotype 1/2c derived once from 1/2a, with reference strain EGDe (1/2a) likely representing an intermediate evolutionary state. In contrast to housekeeping genes, the virulence factor internalin (InlA) evolved by localized recombination resulting in a mosaic pattern, with convergent evolution indicative of natural selection towards a truncation of InlA protein. This work provides a reference evolutionary framework for future studies on L. monocytogenes epidemiology, ecology, and virulence

Measurements of fiducial and differential cross sections for Higgs boson production in the diphoton decay channel at s√=8 TeV with ATLAS

Measurements of fiducial and differential cross sections are presented for Higgs boson production in proton-proton collisions at a centre-of-mass energy of s√=8 TeV. The analysis is performed in the H → γγ decay channel using 20.3 fb−1 of data recorded by the ATLAS experiment at the CERN Large Hadron Collider. The signal is extracted using a fit to the diphoton invariant mass spectrum assuming that the width of the resonance is much smaller than the experimental resolution. The signal yields are corrected for the effects of detector inefficiency and resolution. The pp → H → γγ fiducial cross section is measured to be 43.2 ±9.4(stat.) − 2.9 + 3.2 (syst.) ±1.2(lumi)fb for a Higgs boson of mass 125.4GeV decaying to two isolated photons that have transverse momentum greater than 35% and 25% of the diphoton invariant mass and each with absolute pseudorapidity less than 2.37. Four additional fiducial cross sections and two cross-section limits are presented in phase space regions that test the theoretical modelling of different Higgs boson production mechanisms, or are sensitive to physics beyond the Standard Model. Differential cross sections are also presented, as a function of variables related to the diphoton kinematics and the jet activity produced in the Higgs boson events. The observed spectra are statistically limited but broadly in line with the theoretical expectations

Evidence for the Higgs-boson Yukawa coupling to tau leptons with the ATLAS detector

Results of a search for H → τ τ decays are presented, based on the full set of proton-proton collision data recorded by the ATLAS experiment at the LHC during 2011 and 2012. The data correspond to integrated luminosities of 4.5 fb−1 and 20.3 fb−1 at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV respectively. All combinations of leptonic (τ → `νν¯ with ` = e, µ) and hadronic (τ → hadrons ν) tau decays are considered. An excess of events over the expected background from other Standard Model processes is found with an observed (expected) significance of 4.5 (3.4) standard deviations. This excess provides evidence for the direct coupling of the recently discovered Higgs boson to fermions. The measured signal strength, normalised to the Standard Model expectation, of µ = 1.43 +0.43 −0.37 is consistent with the predicted Yukawa coupling strength in the Standard Model

Construction and test of a fine-grained liquid argon preshower prototype

A separate liquid argon preshower detector consisting of two layers featuring a fine granularity of 2.5~10$^{\mathrm{-3}}$ was studied by the RD3 collaboration. A prototype covering approximately 0.8 in pseudo-rapidity and 9 degrees in azimuth was built and tested at CERN in July 94. CMOS and GaAs VLSI preamplifiers were designed and tested for this occasion. The combined response of this detector and an accordion electromagnetic calorimeter prototype to muons, electrons and photons is presented. For minimum ionizing tracks a signal-to-noise ratio of 4.5 per preshower layer was measured. Above 150~GeV the space resolution for electrons is better than 250~$\mu$m in both directions. The precision on the electromagnetic shower direction, determined together with the calorimeter, is better than 4 mrad above 50~GeV. It is concluded that the preshower detector would adequately fulfil its role for future operation at CERN Large Hadron Collider