The Pyrocarbon Deposition Techniques of Mechanical Heart Valve Prostheses

The structure and property of pyrocarbon varies widely with different deposition conditions. The isotropic carbon which can only been deposited in the bed of fluidized particles is very important in biomedical fields, for instance, it is often used as the coating of artificial heart valve components. The deposition of isotropic pyrocarbon containing silicon is experimented in fluidized bed over a wide range of deposition conditions. The results show that bed temperature influences strongly average coating rate, coating density, silicon content and coating micro-hardness. Propane concentration has a much effect on coating density, carbon matrix density and isotropic characteristics. Total gas flow rate and inlet dimension of fluidized bed affect the formation of fluidized bed.

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In Vitro Hemolysis by Mechanical Heart Valve Prostheses with Tilting Disc

The International Journal of Artificial Organs ◽

10.1177/039139889201501112 ◽

1992 ◽

Vol 15 (11) ◽

pp. 681-685 ◽

Cited By ~ 1

Author(s):

M.O. Wendt ◽

M. Pohl ◽

S. Pratsch ◽

D. Lerche

Keyword(s):

Heart Valve ◽

Test Chamber ◽

Mechanical Heart Valve ◽

Hemoglobin Concentration ◽

Clinical Results ◽

Artificial Heart Valve ◽

Valve Prosthesis ◽

Heart Valve Prostheses ◽

Valve Prostheses

Hemolytic and subhemolytic blood damage by mechanical heart valve prostheses have been observed in both clinical and in vitro investigations. A direct comparison between these studies is not possible. Nevertheless the transfer of some in vitro results to the behaviour of the valve in situ may be performed considering the similarity principle. This requires the use of dimensionless similarity numbers such as the plasma's hemoglobin concentration (PHb) or others, instead of dimensioned parameters. To evaluate the in vitro hemolysis of valve prosthesis a test chamber filled with human banked blood was used. An artificial ventricle ensuring an oscillatory flow through the valve was also used. The rise of PHb was evaluated in terms of a similarity number, called the lysis number. This number describes the probability of destroying a single red blood cell participating once in the hemolytic process under consideration. The lysis number, a Björk-Shiley valve (TAD 29), was found to be in the order of 2 × 10−4. From this, the survival time of erythrocytes in patients with an artificial heart valve was estimated. It was found to be in the order of 20 d of T50 Cr in agreement with clinical results

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Internally Circulating Fluidized Bed Reactor Using m-ZrO2 Supported NiFe2O4 Particles for Thermochemical Two-Step Water Splitting

Journal of Solar Energy Engineering ◽

10.1115/1.4001154 ◽

2010 ◽

Vol 132 (2) ◽

Cited By ~ 12

Author(s):

Nobuyuki Gokon ◽

Hiroki Yamamoto ◽

Nobuyuki Kondo ◽

Tatsuya Kodama

Keyword(s):

Fluidized Bed ◽

Water Splitting ◽

Gas Flow ◽

Circulating Fluidized Bed ◽

Fluidized Bed Reactor ◽

Thermal Reduction ◽

Input Power ◽

Light Irradiation ◽

Bed Temperature ◽

N2 Flow Rate

A windowed internally circulating fluidized bed reactor was tested using m-ZrO2-supported NiFe2O4(NiFe2O4/m-ZrO2) particles as redox material for thermochemical two-step water splitting to produce hydrogen from water. The internally circulating fluidized bed of NiFe2O4/m-ZrO2 particles is directly heated by solar-simulated Xe light irradiation through a transparent quartz window mounted on top of the reactor. A sun simulator with three Xe lamps at laboratory scale has been newly installed in our laboratory for testing the fluidized bed reactor. The input power of incident Xe light can be scaled up to 2.6 kWth. Temperature distributions within the fluidized bed are measured under concentrated Xe light irradiation with an input power of 2.6 kWth. Hydrogen productivity and reactivity for the fluidized bed of NiFe2O4/m-ZrO2 particles are examined using two different reactors under the N2 flow rate and flow ratio, which yield a higher bed temperature. The feasibility of successive two-step water splitting using the fluidized bed reactor is examined by switching from N2 gas flow in the thermal reduction step to a steam/N2 gas mixture in the water decomposition step. It is confirmed that hydrogen production takes place in the single fluidized bed reactor by successive two-step water splitting.

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Attrition Behavior of Coal Ash Under Circulating Fluidized Bed Combustion Conditions

17th International Conference on Fluidized Bed Combustion ◽

10.1115/fbc2003-129 ◽

2003 ◽

Author(s):

Franz Winter ◽

Xin Liu

Keyword(s):

Fluidized Bed ◽

Circulating Fluidized Bed ◽

Coal Ash ◽

Operating Conditions ◽

Laboratory Scale ◽

Silica Sand ◽

Electrical Heating ◽

Fluidized Bed Combustion ◽

Bed Temperature ◽

Wide Range

The attrition behavior of ash produced from two bituminous and one anthracite coal was studied under laboratory-scale circulating fluidized bed combustor (CFBC) conditions. After the ash was produced in the oven, the ash sample with a size range from 0.1 to 1 mm was fed into the hot CFBC, which was heated by electrical heating shells and fluidized by air. The laboratory-scale CFBC was operated with using fine silica sand (40 to 80 μm) as bed material. After a certain time the operation was stopped, all particles were collected and sieving analysis was performed to obtain the actual particle size distribution (PSD) of the coal ash. The operating conditions were changed in a wide range, i.e. the bed temperature from 600 to 850°C, the fluidizing velocity from 1.2 to 2 m/s, the residence time from 60 to 120 min and the design of the cyclone. The effects of operating conditions and coal type were studied and their relative importance is discussed. Elemental analysis of the coal ashes showed that Si and Ca may play an important role during attrition.

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Emissions of SO3 from a Coal-Fired Fluidized Bed under Normal and Staged Combustion

ISRN Environmental Chemistry ◽

10.1155/2013/514751 ◽

2013 ◽

Vol 2013 ◽

pp. 1-7 ◽

Cited By ~ 4

Author(s):

Wasi Z. Khan ◽

Bernard M. Gibbs ◽

Assem Ayaganova

Keyword(s):

Fluidized Bed ◽

Atmospheric Pressure ◽

Fluidized Bed Combustion ◽

Staged Combustion ◽

Bed Height ◽

Excess Air ◽

Bed Temperature ◽

Wide Range ◽

Level 1 ◽

Secondary Air

This paper reports the measurements of SO3 emissions with and without limestone under unstaged and staged fluidized-bed combustion, carried out on a m2 and 2 m high stainless-steel combustor at atmospheric pressure. The secondary air was injected 100 cm above the distributor. SO3 emissions were monitored for staging levels of 85 : 15, 70 : 30, and 60 : 40, equivalent to a primary air/coal ratio (PACR) of ~0.86, 0.75, and 0.67. Experiments were carried out at 0%–60% excess air level, 1-2 m/s fluidizing velocity, 800–850°C bed temperature, and 20–30 cm bed height. During unstaged combustion runs, SO3 emissions were monitored for a wide range of Ca/S ratios from 0.5 to 13. However, for the staged combustion runs, the Ca/S ratio was fixed at 3. SO3 was retained to a lesser extent than SO2, suggesting that SO2 reacts preferentially with CaO and that SO3 is involved in the sulphation process to a lesser degree. The SO3 emissions were found to be affected by excess air, whereas the fluidizing velocity and bed temperature had little effect. SO3 was depressed on the addition of limestone during both the staged and unstaged operations, and the extent of the reduction was higher under staged combustion.

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Minimum Fluidization Velocity of Intermediate Sized Particles in Conventional and Packed Fluidized Bed

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2018-0321 ◽

2019 ◽

Vol 17 (10) ◽

Cited By ~ 1

Author(s):

Niraj J. Kulkarni ◽

Channamallikarjun S. Mathpati ◽

Debapriya Mandal ◽

Vishwanath H. Dalvi

Keyword(s):

Fluidized Bed ◽

Gas Flow ◽

Industrial Applications ◽

Hydrodynamic Characteristics ◽

Minimum Fluidization Velocity ◽

Fluidization Velocity ◽

Minimum Fluidization ◽

Bed Temperature ◽

Superficial Gas Velocity

Abstract Typical Geldart B class particles are often used in a gas-solid fluidized bed for various industrial applications. The quality of fluidization of Geldart B particles depends upon the geometry of the bed containing vessel, properties of fluidization medium and the gas flow rate. The presence of large bubbles/slugs that can happen in beds with intermediate class particles is undesirable. The bubbling and slugging, which decrease the quality of fluidization can be prevented with the phenomenon called packed fluidization. Experiments were carried out on the conventional fluidized bed and packed fluidized bed to investigate some of the hydrodynamic characteristics as a function of bed temperature, small particle size, fluidization medium and fraction of voids of packing filled with small particles. The superficial gas velocity required for packed fluidization reduces significantly than conventional fluidization. The minimum fluidization velocity of particles increases with an increase in density of the fluidization gas and decreases with increase in temperature of the bed. A correlation established from experimental data fairly predicts the minimum fluidization velocity for the packed fluidized bed.

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A Comparison of a Moderate with Moderate-high Intensity Oral Anticoagulant Treatment in Patients with Mechanical Heart Valve Prostheses

Thrombosis and Haemostasis ◽

10.1055/s-0038-1656064 ◽

1997 ◽

Vol 77 (05) ◽

pp. 0839-0844 ◽

Cited By ~ 34

Author(s):

Vittorio Pengo ◽

Fabio Barbero ◽

Alberto Banzato ◽

Elisabetta Garelli ◽

Franco Noventa ◽

...

Keyword(s):

Heart Valve ◽

High Intensity ◽

Oral Anticoagulant ◽

Oral Anticoagulants ◽

Mechanical Heart Valve ◽

Moderate Intensity ◽

Minor Bleeding ◽

Anticoagulant Treatment ◽

Oral Anticoagulant Treatment ◽

Valve Prostheses

SummaryBackground. The long-term administration of oral anticoagulants to patients with mechanical heart valve prostheses is generally accepted. However, the appropriate intensity of oral anticoagulant treatment in these patients is still controversial.Methods and Results. From March 1991 to March 1994, patients referred to the Padova Thrombosis Center who had undergone mechanical heart valve substitution at least 6 months earlier were randomly assigned to receive oral anticoagulants at moderate intensity (target INR = 3) or moderate-high intensity (target INR = 4). Principal end points were major bleeding, thromboembolism and vascular death. Minor bleeding was a secondary end-point.A total of 104 patients were assigned to the target 3 group and 101 to the target 4 group; they were followed for from 1.5 years to up 4.5 years (mean, 3 years). Principal end-points occurred in 13 patients in the target 3 group (4 per 100 patient-years) and in 20 patients in the target 4 group (6.9 per 100 patient-years). Major hemorrhagic events occurred in 15 patients, 4 in the target 3 group (1.2 per 100 patient-years) and 11 in the target 4 group (3.8 per 100 patient-years) (p = 0.019). The 12 recorded episodes of thromboembolism, 4 of which consisted of a visual deficit, were all transient ischemic attacks, 6 in the target 3 group (1.8 per 100 patient-years) and 6 in the target 4 group (2.1 per 100 patient- years). There were 3 vascular deaths in each group (0.9 and 1 per 100 patient-years for target 3 and target 4 groups, respectively). Minor bleeding episodes occurred 85 times (26 per 100 patient-years) in the target 3 group and 123 times (43 per 100 patient-years) in the target 4 group (p = 0.001).Conclusions. Mechanical heart valve patients on anticoagulant treatment who had been operated on at least 6 months earlier experienced fewer bleeding complications when maintained on a moderate intensity regimen (target INR = 3) than those on a moderate-high intensity regimen (target INR = 4). The number of thromboembolic events and vascular deaths did not differ between the two groups.

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