No abstract
A formula is presented for determining the form of the calibration curve ofaflowmeter within a broad range of Reynolds numbers. The theoretical curves agree well with the experimental results for natural gases. The discrepancies seen for low discharges are related to heat losses in the transducer.In the article [ 1], we explained the design requirements, principle of operation, and general theory of new partial thermal flowmeter "Tsiklon." The flowmeter incorporates the concept of partiality within the framework of the thermal principle of measurement. Partiality is assured by means of a simple device, called a flow divider, which "screws onto" the transducer (the primary sensor) and creates the necessary conditions of flow of the test medium around the thermoprobe.The divider causes a substantial "reduction" in the main flow, which significantly decreases the energy consumed in the measurement of discharge.The mass flow rate G of a gas (or liquid) is determined by the power W needed to maintain a constant temperature difference AT between the thermoprobe-transducer and the test medium. Different values of AT may be specified (depending on the range of discharges being measured). A secondary electronic device automatically keeps the temperature difference constant by regulating the voltage supplied to the thermistor (heater). We will examine the principles behind the construction of the calibration curve W(G) of the instrument and discuss inherent limitations on its capabilities in the regions of small and large discharges.The relation W(G) (calibration curve) is constructed on the basis of the sequential use of formulas presented in this article. The same formulas will be used simultaneously in the discussion of the discharge measurement range of the given instrument.The flowmeter is designed to measure the mass flow rate of a gas (liquid) G (in kilograms per second), which is connected with the volume flow rate Q (in cubic meters per second) by the relation G=p vS=p Q=pnQ n,where p is the density of the medium; v is the velocity of the main flow (pv is mass velocity); S = (I/4)r~D 2 (D is the inside diameter of the pipe); the quantities Pn and Qn pertain to normal conditions (20~ 1.013 bars). The mass flow rate G corresponds to the value of the Reynolds number Re for the main flowwhere p. is the absolute viscosity of the medium. The following formula was obtained in [1] for the Reynolds number of the partial flow in the divider washing over the thermoprobe of the instrument (in a gap with the characteristic dimension d2u -ds)
Aim To identify clinical differences between patients on the heart transplant waiting list (HTWL) in the origin of chronic heart failure (CHF).Materials and methods From January 2010 through September 2019, 235 patients (age, 47+13 years (from 10 to 67 years); men, 79% (n=186)) were included in the HTWL. The patients were divided into two groups; group 1 (n=104, 44 %) consisted of patients with ischemic heart disease (IHD); group 2 (n=131, 56 %) included patients with noncoronarogenic CHF. Clinical and instrumental data and frequency of the mechanical circulatory support (MCS) as a “bridge” to heart transplantation (HT) were retrospectively evaluated.Results Group 1 included more male patients than group 2 [97 % (n=101) and 82 % (n=85), р<0.0001]; patients were older (54±8 and 42±14 years, р=0.0001). On inclusion into the HTWL, the CHF functional class was comparable in the groups, III [III;IV]; there were more patients of the UNOS 2 class in group 1 than in group 2 [75 % (n=78) and 57 % (n=75), р=0.005]. Patient distribution in UNOS 1B and 1A classes was comparable in the groups: 21% (n=22) and 3% (n=4) in group 1 and 33 % (n=43) and 10 % (n=13) in group 2. According to echocardiography patients of group 1 compared to group 2 showed a tendency towards higher values of left ventricular ejection fraction (Simpson method) [22 [18;26] % and 19 [15;24] %, р=0.37] and stroke volume [59 [44;72] % and 50 [36;67] %, р=0.07]. Numbers of patients with a cardioverter defibrillator or a cardiac resynchronization device with a defibrillator function were comparable in the groups [35 % (n=36) and 34 % (n=45)]. Comparison of comorbidities in groups 1 and 2 showed higher incidences of pulmonary hypertension [55 % (n=57) and 36 % (n=47), р=0.005], obesity [20 % (n=21) and 10 % (n=13), р=0.03], and type 2 diabetes mellitus [29 % (n=30) and 10 % (n=13), р=0.0004]. Rates of chronic obstructive lung disease, stroke, chronic kidney disease and other diseases were comparable. Duration of staying on the HTWL was comparable (104 [34; 179] and 108 [37; 229] days). During staying on the HTWL, patients of group 1 less frequently required MCS implantation [3 % (n=3) and 28 % (n=21), р=0.0009]. HT was performed for 59 % patients (n=61) in group 2 and 52 % (n=69) patients in group 2. Death rate in the HTWL was lower in group 1 [13 % (n=14) and 27 % (n=35), р<0.01].Conclusion On inclusion into the HTWL, patients with noncoronarogenic CHF had more pronounced CHF manifestations and a more severe UNOS class but fewer comorbidities than patients with CHF of ischemic origin. With a comparable duration of waiting for HT, patients with noncoronarogenic CHD more frequently required MCS implantation and had a higher death rate.
Objective: to estimate the survival of patients in the heart transplantation waiting list (HTx WL) at Almazov National Medical Research Centre (V.A. Almazov NMRC), Saint-Petersburg, Russia, from 2010 to 2018 and to define factors for death among these patients.Materials and methods: it was a single-centre retrospective study involving 151 patients with end-stage chronic heart failure (CHF) classes III-IV (NYHA) in the HTx WL.Results: the dynamic of decreasing mortality was revealed. Based on the results of constructing the discriminant function, four factors predicting the survival of patients in the HTx WL, namely, ACE inhibitors/ARBs, beta-blockers, status 1 of UNOS, CHF NYHA class IV, were pointed out. The model has sufficient resolving power but is not capable of predicting the outcome in the presence of acute decompensation of CHF.Conclusion: mortality in the HTx WL for the period 2010-2018 decreased that was associated with an active implementation of cardiac surgical methods as a «bridge» to transplant and optimal medical therapy, including ACE inhibitors/ARBs and beta-blockers in patients supported with inotropes (UNOS 1B). The greatest risk of mortality was found in CHF class IV and status 1 by UNOS.
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