Liquid Saturation and Gas-Liquid Distribution in Multiphase Monolithic Reactors

The Monolith Bed is One of the Promising Catalytic Reactors for a Number of Chemical Gas-Liquid-Solid Processes. in the Present Work, Liquid Saturations for Five Different Monoliths Have Been Investigated Experimentally in a Cold-Flow Unit with a Reactor Diameter of 5.0 Cm. the Influences of Gas and Liquid Flow Rates and of the Direction of Two-Phase Flow on Liquid Saturation Were Examined. the Results Indicate that the Direction of Flow Has No Significant Influence on Liquid Saturation for Proper Gas-Liquid Distribution. the Experimental Results Are in Good Agreement with Predictions of the Drift Flux Model using the Distribution Parameter Proposed by Ishii (ANL Report ANL-77-47, 1977) Along with the Assumption of Zero Drift Velocity. in Preliminary Experiments, Gamma-Ray Computed Tomography (CT) Has Been Successfully Applied to Measure Time-Averaged Liquid Distribution over the Monolith Cross-Section in a Selected Condition. the Employment of a Nozzle-Type Distributor Provides an Almost Uniform Liquid Distribution over the Monolith Substrate. It is Demonstrated that CT is a Viable Technique for Studying Two-Phase Flow in Laboratory-Scale Monolith Reactors. © 2005 Elsevier Ltd. All Rights Reserved

Impact of the indexed effective orifice area on mid-term cardiac-related mortality after aortic valve replacement

Background There has been ongoing controversy as to whether prosthesis-patient mismatch (PPM, defined as indexed effective orifice area (EOAI) <0.85 m(2)/cm(2)) influences mortality after aortic valve replacement (AVR). In most studies, PPM is anticipated by reference tables based on mean EOAs as opposed to individual assessment. These reference values may not reflect the actual in vivo EOAI and hence, the presence or absence of PPM may be based on false assumptions. Objective To assess the impact of small prosthesis EOA on survival after aortic valve replacement AVR. Methods 645 patients had undergone an AVR between 2000 and 2007 entered the study. All patients underwent transthoracic echocardiography for determination of the actual EOAI within 6 months postoperatively. In order to predict time from surgery to death a proportional hazards model for competing risks (cardiac death vs death from other causes) was used. EOAI was entered as a continuous variable. Results PPM occurred in 40% of the patients. After a median follow-up of 2.35 years, 92.1% of the patients were alive. The final Cox regression model showed a significantly increased risk for cardiac death among patients with a smaller EOAI (HR=0.32, p=0.022). The effect of EOAI on the 2-5 year mortality risk was demonstrated by risk plots. Conclusions In contrast to previous studies these EOAI values were obtained through postoperative echocardiography, substantially improving the accuracy of measurement, and the EOAI was modelled as a continuous variable. There was a significantly improved survival for larger EOAIs following AVR. Strategies to avoid PPM should become paramount during AVR

Neurologic sequelae of the donor arm after endoscopic versus conventional radial artery harvesting

ObjectiveEndoscopic radial artery harvesting remarkably improves cosmetic results after coronary artery bypass surgery. The aim of this study was to investigate neurologic sequelae of the donor arm compared with those occurring after the conventional harvesting technique.MethodsFifty-three patients who had undergone endoscopic radial artery harvesting were followed up 1 year after the coronary artery bypass operation by means of questionnaire analysis and clinical neurologic investigation (ENDO group). Fifty-three patients who had conventional radial artery harvesting during the same time frame served as control subjects (OPEN group).ResultsPostoperative wound revision was required in 4 patients of the OPEN group (P = .045 vs the ENDO group). Neurologic symptoms of the donor arm were present in 22 (OPEN group) versus 34 (ENDO group) patients (P = .020): a lesion of the superficial radial nerve was shown in 12 (OPEN group) versus 24 (ENDO) patients (P = .014), and a lesion of the lateral antebrachial cutaneous nerve occurred only in the control group in 12 patients (P < .001). Paraesthesia without impaired sensibility was present in 3 (OPEN group) versus 10 (ENDO group) patients (P = .038). Clinical investigation revealed that temperature, pain, and touch sensation, as well as spatial discrimination, were equally impaired in symptomatic patients, whereas vibration sensation was not affected.ConclusionAfter endoscopic radial artery harvesting, impaired sensibility in the region of the superficial radial nerve and paresthesia are more frequent than after the open procedure. However, in contrast to the sequelae of the open procedure, wound revision and injury of the lateral antebrachial cutaneous nerve did not occur. Because of the excellent cosmetic results and avoidance of wound complications, we have opted to use endoscopic radial artery harvesting as the technique of choice, despite the higher incidence of sensory disturbances

Exercise hemodynamics of bovine versus porcine bioprostheses: A prospective randomized comparison of the mosaic and perimount aortic valves

ObjectiveThis prospective randomized study compares a porcine with a bovine bioprosthesis in the aortic position with regard to hemodynamic performance during exercise.MethodsBetween August of 2000 and December of 2002, 136 patients underwent aortic valve replacement with the porcine Medtronic Mosaic (n = 66) or the bovine Carpentier-Edwards Perimount (n = 70) bioprosthesis. Transthoracic echocardiography was performed to assess hemodynamic and dimensional data preoperatively and 10 months postoperatively; the latter follow-up included stress echocardiography with treadmill exercise.ResultsAt rest and during exercise (25 and 50 W), there was a significant difference in mean pressure gradient between the bovine and the porcine valves with labeled sizes 21 and 23, with superiority of the Perimount prosthesis. There was no difference in effective orifice area and incidence of patient-prosthesis mismatch among all sizes. The left ventricular mass index decreased significantly within 10 months postoperatively in the size 23 bovine group and the size 25 porcine group.ConclusionsOur data show a significant superiority of pressure gradients for the bovine bioprosthesis, especially with small valve sizes, when compared with the porcine device, which is more distinctive during exercise

Patency rates of endoscopically harvested radial arteries one year after coronary artery bypass grafting

ObjectivesTo improve patients’ acceptance of the radial artery as a graft for coronary revascularization, we introduced an endoscopic harvesting technique. The aim of this study was to assess graft quality 1 year after the operation.MethodsIn 50 patients who underwent endoscopic radial artery harvesting for coronary artery bypass grafting, 64-slice computed tomography, electrocardiography, and echocardiography were utilized to assess graft patency and left ventricle function at a 1-year follow-up. In addition, the influencing factors of radial artery graft patency were evaluated. Radial artery patency was compared with a control group from our database.ResultsAny patency of endoscopically harvested radial artery grafts was 78% (39/50) and perfect patency was 72% (36/50) 1 year after coronary revascularization. The implanting surgeon and graft harvester, patient factors, graft properties, medication, and target territory did not influence the patency rates of the radial artery graft. The only significant and strong parameter to predict perfect graft patency was the severity of the target vessel stenosis (P < .001). In patients with a target vessel stenosis of 90% or greater, radial artery graft patency was 90.3% (28/31). Patency rates of endoscopically (72%) and conventionally (74%) harvested radial arteries were not different (P = .822).ConclusionsPatency rates 1 year after endoscopic radial artery harvesting are comparable to the open technique. On the basis of our results, we attempt to use the radial artery as a bypass graft only for target coronary arteries with 90% or greater stenosis. We recommend endoscopic harvesting as the technique of choice to harvest the radial artery

First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto- noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of 11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initial outliers, further studies show no significant evidence for the presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the median upper limit across the search bands is below the spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried out so far

First measurement of the Hubble Constant from a Dark Standard Siren using the Dark Energy Survey Galaxies and the LIGO/Virgo Binary–Black-hole Merger GW170814

International audienceWe present a multi-messenger measurement of the Hubble constant H 0 using the binary–black-hole merger GW170814 as a standard siren, combined with a photometric redshift catalog from the Dark Energy Survey (DES). The luminosity distance is obtained from the gravitational wave signal detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo Collaboration (LVC) on 2017 August 14, and the redshift information is provided by the DES Year 3 data. Black hole mergers such as GW170814 are expected to lack bright electromagnetic emission to uniquely identify their host galaxies and build an object-by-object Hubble diagram. However, they are suitable for a statistical measurement, provided that a galaxy catalog of adequate depth and redshift completion is available. Here we present the first Hubble parameter measurement using a black hole merger. Our analysis results in , which is consistent with both SN Ia and cosmic microwave background measurements of the Hubble constant. The quoted 68% credible region comprises 60% of the uniform prior range [20, 140] km s−1 Mpc−1, and it depends on the assumed prior range. If we take a broader prior of [10, 220] km s−1 Mpc−1, we find (57% of the prior range). Although a weak constraint on the Hubble constant from a single event is expected using the dark siren method, a multifold increase in the LVC event rate is anticipated in the coming years and combinations of many sirens will lead to improved constraints on H 0