858 research outputs found

    Sub-Nyquist Field Trial Using Time Frequency Packed DP-QPSK Super-Channel Within Fixed ITU-T Grid

    Full text link
    Sub-Nyquist time frequency packing technique was demonstrated for the first time in a super channel field trial transmission over long-haul distances. The technique allows a limited spectral occupancy even with low order modulation formats. The transmission was successfully performed on a deployed Australian link between Sydney and Melbourne which included 995 km of uncompensated SMF with coexistent traffic. 40 and 100 Gb/s co-propagating channels were transmitted together with the super-channel in a 50 GHz ITU-T grid without additional penalty. The super-channel consisted of eight sub-channels with low-level modulation format, i.e. DP-QPSK, guaranteeing better OSNR robustness and reduced complexity with respect to higher order formats. At the receiver side, coherent detection was used together with iterative maximum-a-posteriori (MAP) detection and decoding. A 975 Gb/s DP-QPSK super-channel was successfully transmitted between Sydney and Melbourne within four 50GHz WSS channels (200 GHz). A maximum potential SE of 5.58 bit/s/Hz was achieved with an OSNR=15.8 dB, comparable to the OSNR of the installed 100 Gb/s channels. The system reliability was proven through long term measurements. In addition, by closing the link in a loop back configuration, a potential SE*d product of 9254 bit/s/Hz*km was achieved

    Early and long-term outlook of percutaneous coronary intervention for bifurcation lesions in young patients

    Get PDF
    Coronary artery disease is most common in older patients, but may occur in younger subjects. The outlook of young patients after percutaneous coronary intervention (PCI) of challenging lesion subsets such as coronary bifurcations, is not established. We thus aimed to appraise the early and long-term results of PCI for bifurcations in young patients

    Transcatheter aortic valve implantation in failed bioprosthetic surgical valves.

    Get PDF
    IMPORTANCE: Owing to a considerable shift toward bioprosthesis implantation rather than mechanical valves, it is expected that patients will increasingly present with degenerated bioprostheses in the next few years. Transcatheter aortic valve-in-valve implantation is a less invasive approach for patients with structural valve deterioration; however, a comprehensive evaluation of survival after the procedure has not yet been performed. OBJECTIVE: To determine the survival of patients after transcatheter valve-in-valve implantation inside failed surgical bioprosthetic valves. DESIGN, SETTING, AND PARTICIPANTS: Correlates for survival were evaluated using a multinational valve-in-valve registry that included 459 patients with degenerated bioprosthetic valves undergoing valve-in-valve implantation between 2007 and May 2013 in 55 centers (mean age, 77.6 [SD, 9.8] years; 56% men; median Society of Thoracic Surgeons mortality prediction score, 9.8% [interquartile range, 7.7%-16%]). Surgical valves were classified as small (≤21 mm; 29.7%), intermediate (>21 and <25 mm; 39.3%), and large (≥25 mm; 31%). Implanted devices included both balloon- and self-expandable valves. MAIN OUTCOMES AND MEASURES: Survival, stroke, and New York Heart Association functional class. RESULTS: Modes of bioprosthesis failure were stenosis (n = 181 [39.4%]), regurgitation (n = 139 [30.3%]), and combined (n = 139 [30.3%]). The stenosis group had a higher percentage of small valves (37% vs 20.9% and 26.6% in the regurgitation and combined groups, respectively; P = .005). Within 1 month following valve-in-valve implantation, 35 (7.6%) patients died, 8 (1.7%) had major stroke, and 313 (92.6%) of surviving patients had good functional status (New York Heart Association class I/II). The overall 1-year Kaplan-Meier survival rate was 83.2% (95% CI, 80.8%-84.7%; 62 death events; 228 survivors). Patients in the stenosis group had worse 1-year survival (76.6%; 95% CI, 68.9%-83.1%; 34 deaths; 86 survivors) in comparison with the regurgitation group (91.2%; 95% CI, 85.7%-96.7%; 10 deaths; 76 survivors) and the combined group (83.9%; 95% CI, 76.8%-91%; 18 deaths; 66 survivors) (P = .01). Similarly, patients with small valves had worse 1-year survival (74.8% [95% CI, 66.2%-83.4%]; 27 deaths; 57 survivors) vs with intermediate-sized valves (81.8%; 95% CI, 75.3%-88.3%; 26 deaths; 92 survivors) and with large valves (93.3%; 95% CI, 85.7%-96.7%; 7 deaths; 73 survivors) (P = .001). Factors associated with mortality within 1 year included having small surgical bioprosthesis (≤21 mm; hazard ratio, 2.04; 95% CI, 1.14-3.67; P = .02) and baseline stenosis (vs regurgitation; hazard ratio, 3.07; 95% CI, 1.33-7.08; P = .008). CONCLUSIONS AND RELEVANCE: In this registry of patients who underwent transcatheter valve-in-valve implantation for degenerated bioprosthetic aortic valves, overall 1-year survival was 83.2%. Survival was lower among patients with small bioprostheses and those with predominant surgical valve stenosis

    Evaporating waterbody effects in a simplified urban neighbourhood: A RANS analysis

    Get PDF
    The incorporation of nature-based solutions comprising green and blue infrastructure is often touted as a way to cool cities and enhance pollutant removal. However, there is little agreement between different methodologies to measure the effect of any single intervention. Here, we present 3D steady RANS simulations to investigate the influence of waterbody on in-canyon flow structure, temperature (T*) and water vapour (!*) distribution in a simplified urban neighbourhood. A novel solver that captures evaporation effects is developed and validated against wind tunnel experiments. Simulations are performed under neutral atmospheric conditions for forced -and mixed-convection cases and different air-water temperature differences, indicative of either daytime or night-time conditions. Results under forced convection show minimal impact on the flow structure, whilst T* and !* effects are distributed primarily over and around the water surface. However, the mixed-convection case shows that a cooler waterbody weakens the principal vortex in the open square, whilst T* and !* effects reach further upwind and are more widely distributed in the spanwise direction. A warmer waterbody is shown to disrupt the skimming flow structure, indicating a possible heat and pollutant removal mechanism from around the waterbody and also downwind canyons

    The colour of forcing statistics in resolvent analyses of turbulent channel flows

    Full text link
    The cross-spectral density (CSD) of the non-linear forcing in resolvent analyses is here quantified for the first time for turbulent channel flows. Direct numerical simulations (DNS) at Reτ=179Re_{\tau} =179 and Reτ=543Re_{\tau} =543 are performed. The CSDs are computed for highly energetic structures typical of buffer-layer and large-scale motions, for different temporal frequencies. The CSD of the non-linear forcing is shown not to be uncorrelated (white) in space, which implies the forcing is structured. Since the non-linear forcing is non-solenoidal by construction and the velocity of an incompressible flow is affected only by the solenoidal part of the forcing, this solenoidal part is evaluated. It is shown that the solenoidal part of the non-linear forcing is the combination of oblique streamwise vortices and a streamwise component which counteract each other, as in a destructive interference. It is shown that a rank-2 approximation of the forcing, with only the most energetic SPOD (spectral proper orthogonal decomposition) modes, leads to the bulk of the response. The projections of the non-linear forcing onto the right-singular vectors of the resolvent are evaluated. The left-singular vectors of the resolvent associated with very low-magnitude singular values are non-negligible since the non-linear forcing term has a non-negligible projection onto the linear sub-optimals of resolvent analysis. The same projections are computed when the forcing is modelled with an eddy-viscosity approach. It is clarified that this modelling improves the accuracy of the prediction since the projections are closer to those associated with the non-linear forcing from DNS data

    From building regulations and local health rules to the new local building codes. A national survey in Italy on the prescriptive and performance requirements for a new performance approach

    Get PDF
    BACKGROUND: World Health Organization has highlighted the need to strengthen the relationship between health and built environment factors, such as inappropriate housing conditions. Building Regulations and Local Health Rules provide safety and building hygiene in construction practices. Currently the Italian Government is giving rise to a Building Regulation Type and the paper aims to verify the present contents of recent innovative Local Health Rules and Building Regulations of several Italian municipalities for supporting the performance approach of the future Building Regulations including hygienic issues. METHODS: The analysis examines both Building Regulations and Local Health Rules of a sample of about 550 cities, analysing some specific fields of interest: urban field, outdoor issues, housing features, housing restrictions, and qualitative aspects. RESULTS: The analysis focuses on some specific aspects defining the general data reported in Building Regulations and Local Health Rules, in particular around surfaces, heights, lighting and aeration ratio, basements and semi-basements, gas radon, building greenery, etc. CONCLUSION: The investigation permitted to have a wide vision on the present State of the Art in order to highlight some innovative aspects and design approaches of Building Regulations and Local Health Rules. New perspectives in the new regulations should have a performance approach, starting also from the recent SARS-CoV-2 pandemic

    Assessment of coronary atherosclerosis by IVUS and IVUS-based imaging modalities: progression and regression studies, tissue composition and beyond

    Get PDF
    Cardiovascular disease remains the leading cause of mortality, morbidity and disability in the developed world, predominantly affecting the adult population. In the early 1990s coronary heart disease (CHD) was established as affecting one in two men and one in three women by the age of forty. Despite the dramatic progress in the field of cardiovascular medicine in terms of diagnosis and treatment of heart disease, modest improvements have only been achieved when the reduction of cardiovascular mortality and morbidity indices are assessed. To better understand coronary atherosclerosis, new imaging modalities have been introduced. These novel imaging modalities have been used in two ways: (1) for the characterization of plaque types; (2) for the assessment of the progression and regression of tissue types. These two aspects will be discussed in this review

    Multislice computed tomography SYNTAX score for coronary artery disease evaluation prior to transcatheter aortic valve implantation

    Get PDF
    Background: Coronary computed tomography angiography (CCTA) is a useful tool for the evaluation of coronary anatomy prior to both surgical and transcatheter aortic valve implantation (TAVI). Multislice Computed Tomography (MSCT) SYNTAX score (SXscore) strongly correlates with the traditional angiographic SXscore, and the latter has proven to predict cardiovascular events in patients with coronary artery disease (CAD) referred to TAVI. Purpose: The aim of the study is to evaluate the feasibility and accuracy of the calculation of MSCT SXscore in TAVI patients, compared to the gold standard angiographic SXscore. Materials and methods: We evaluated 65 patients eligible for TAVI who underwent both CCTA and invasive coronary angiography (ICA) prior to valve replacement. CCTA was compared to ICA in terms of sensitivity, specificity, and positive and negative predictive values. CCTA performance was evaluated at 3 levels: patient level, vessellevel and segmentlevel. MSCT SXscore was calculated, when possible (i.e. only in fullyevaluable scans), and compared to the angiographic SXscore. Results: Overall CCTA diagnostic performance was good, with high sensitivity and negative predictive values (97.2% and 96.0%, respectively) and good agreement with ICA (k=0.81). As expected, specificity and positive predictive values were lower (82.8% and 87.5%, respectively). At vessellevel, the circumflex artery (CA) was more often misdiagnosed than the other arteries. We were able to calculate MSCT SXscore in 50/65 scans (76.9%). The correlation between MSCT and angiographic SXscore was excellent (Pearson's R=0.965, P<0.001). Conclusions: MSCT SXscore emerges as an interesting tool with strong agreement with angiographic SXscore, providing a noninvasive ambulatory alternative to assess CAD severity in TAVI patients
    corecore