Biomedical subjects

H Y Yuan

Publications and source records attributed to H Y Yuan.

16 recordsLinked to original sources

PubMed2003

A novel permanent maglev impeller TAH: most requirements on blood pumps have been satisfied.

Based on the development of an impeller total artificial heart (TAH) (1987) and a permanent maglev (magnetic levitation) impeller pump (2002), as well as a patented magnetic bearing and magnetic spring (1996), a novel permanent maglev impeller TAH has been developed. The device consists of a rotor and a stator. The rotor is driven radially. Two impellers with different dimensions are fixed at both the ends of the rotor. The levitation of the rotor is achieved by using two permanent magnetic bearings, which have double function: radial bearing and axial spring. As the rotor rotates at a periodic changing speed, two pumps deliver the pulsatile flow synchronously. The volume balance between the two pumps is realized due to self-modulation property of the impeller pumps, without need for detection and control. Because the hemo-dynamic force acting on the left impeller is larger than that on the right impeller, and this force during systole is larger than that during diastole, the rotor reciprocates axially once a cycle. This is beneficial to prevent the thrombosis in the pump. Furthermore, a small flow via the gap between stator and rotor from left pump into right pump comes to a full washout in the motor and the pumps. Therefore, it seems neither mechanical wear nor thrombosis could occur. The previously developed prototype impeller TAH had demonstrated that it could operate in animal experiments indefinitely, if the bearing would not fail to work. Expectantly, this novel permanent magnetic levitation impeller TAH with simplicity, implantability, pulsatility, compatibility and durability has satisfied the most requirements on blood pumps and will have more extensive applications in experiments and clinics.

Heart, Artificial↗

PubMed2002

Recent progress in developing durable and permanent impeller pump.

Since 1980s, the author's impeller pump has successively achieved the device implantability, blood compatibility and flow pulsatility. In order to realize a performance durability, the author has concentrated in past years on solving the bearing problems of the impeller pump. Recent progress has been obtained in developing durable and permanent impeller blood pumps. At first, a durable impeller pump with rolling bearing and purge system has been developed, in which the wear-less rollers made of super-high-molecular weight polythene make the pump to work for years without mechanical wear; and the purge system enables the bearing to work in saline and heparin, and no thrombus therefore could be formed. Secondly, a durable centrifugal pump with rolling bearing and axially reciprocating impeller has been developed, the axial reciprocation of rotating impeller makes the fresh blood in and out of the bearing and to wash the rollers once a circle; in such way, no thrombus could be formed and no fluid infusion is necessary, which may bring inconvenience and discomfort to the receptors. Finally, a permanent maglev impeller pump has been developed, its rotor is suspended and floating in the blood under the action of permanent magnetic force and nonmagnetic forces, without need for position measurement and feed-back control. In conclusion, an implantable, pulsatile, and blood compatible impeller pump with durability may have more extensive applications than ever before and could replace the donor heart for transplantation in the future.

Blood↗

PubMed2001

[The tissue culture of medicinal plant Trichosanthes kirilowii and its protein analysis].

We reported preliminary results of rapid propagation, callus induction and regeneration of Trichosanthes Kirilowii, and its protein analysis. Pre-existing meristerms regenerate shoots very rapidly when grown on MS medium containing 0.5 or 1.0 mg/L 6-BA; calli could be induced from leaf sections when put on MS medium containing 4.0 mg/L 6-BA + 0.2 mg/L IAA; shoots regenerated successfully 30 days after calli induction and the differentiation ratio was one shoot out of every four leaf sections; and all shoots gave rise to roots after removing onto MS medium containing 0.1 mg/L NAA and 100% survived when transplanted into soil. Very excitingly, these plants produced small tubers in one month, where satisfactory expression of TCS protein was detected by Western blot analysis.

Culture Media↗

PubMed2000

[The diploid of genetically engineered yeast for expression of hybrid HBsAg gene SA-28].

By mating a yeast haploid expressing hybrid HBsAg gene SA-28, Y19/YFD158, with another hapolid Y95, the diploid Y95xY19/YFD158 was constructed. The experiments showed that the cell density of the diploid in fermentation was three time higher than that of the haploid, the stability of expression vector in the diploid was much higher than in the haploid, the xpression level of hybrid HBsAg gene of the diploid was more than three time higher than that of the haploid and the average cope number in diploid cell was a little lower than that in the haploid.

Diploidy↗

PubMed2000

[Effects of gene copy number and chromosomal position on the expression of a modified HBsAg gene SA-28 in yeast].

The effect of gene copy number and chromosomal position on heterologous gene expression in Saccharomyces cerevisae has been tentatively investigated using a modified hepatitis B virus surface antigen SA-28 gene. The plasmids containing different copies of SA-28 gene expression cassette were integrated into different chromosomal loci via FLP recombinase mediated targeted integration. The expression of SA-28 gene in the resultant transformants was then measured. The result indicated that the expression of SA-28 gene was positively related to the gene dosage at HIS3 locus and had chromosomal polarity at several chromosomal loci.

Chromosome Mapping↗

PubMed1992

The design of a two-part acid-etched resin-bonded fixed partial denture.

A new framework design is presented for resin-bonded, acid-etched, fixed partial dentures. This innovative design divided the restoration into two parts, each with a separate path of insertion. The preparation of abutment teeth required minimal reduction and the pontic could not be displaced during function. Thirty-five patients with missing posterior teeth have been treated with this imaginative approach and after approximately 2 years, there have been no debonding failures.

Acid Etching, Dental↗

PubMedDate not supplied

Measurement of rotary pump flow and pressure by computation of driving motor power and speed.

Measurement of pump flow and pressure by ventricular assist is an important process, but difficult to achieve. On one hand, the pump flow and pressure are indicators of pump performance and the physiologic status of the receptor, meanwhile providing a control basis of the blood pump itself. On the other hand, the direct measurement forces the receptor to connect with a flow meter and a manometer, and the sensors of these meters may cause haematological problems and increase the danger of infection. A novel method for measuring flow rate and pressure of rotary pump has been developed recently. First the pump performs at several rotating speeds, and at each speed the flow rate, pump head and the motor power (voltage x current) are recorded and shown in diagrams, thus obtaining P (motor power)-Q (pump volume) curves as well as P-H (pump head) curves. Secondly, the P, n (rotating speed) values are loaded into the input layer of a 3-layer BP (back propagation) neural network and the Q and H values into the output layer, to convert P-Q and P-H relations into Q = f (P,n) and H = g (P, n) functions. Thirdly, these functions are stored by computer to establish a database as an archive of this pump. Finally, the pump flow and pressure can be computed from motor power and speed during animal experiments or clinical trials. This new method was used in the authors' impeller pump. The results demonstrated that the error for pump head was less than 2% and that for pump flow was under 5%, so its accuracy is better than that of non-invasive measuring methods.

Animals↗

PubMedDate not supplied

Axial reciprocation of rotating impeller: a new concept of antithrombogenecity in centrifugal pump.

For long-term application, rotary pumps have to solve the problems of bearing wear and thrombosis along the bearing. Most investigators choose the magnetic bearing to realize zero-friction and no contact between the rotor and stator; the former avoids the mechanical wear and the latter eliminates the possibility of thrombus formation. The authors have tried and found, however, that it is difficult to apply a magnetic bearing to the rotary pump without disturbing its simplicity, reliability and implantability, and have therefor developed a much simpler and much more creative approach to achieve the same results. Instead of using a sliding bearing, a rolling bearing has been devised for the pump, and its friction is about 1/15 of the sliding bearing. Furthermore, a wear-proof material of ultra-high-molecular weight polythene has been adopted to make the rollers, and its anti-wear property is 8 times better than metal. Thereby, the service life of the bearing has been prolonged to ten years according to the documents provided by the producer. In order to prevent the thrombus formation along the bearing, the impeller reciprocates axiallly as the impeller changes its rotating speed periodically to produce a pulsatile flow. The reciprocation is the result of the effects of a magnetic force between the motor rotor and stator, and a hydraulic force between the blood flow and the impeller. Similar to a piston pump, the oscillating impeller can make the blood flow in and out of the bearing, resulting in wash-out once a circle. This obviously helps to prevent thombosis along the bearing and in the pump. The endurance tests with saline of this novel pump demonstrated the durabililty of the device. It promises to be able to assist the circulation of patients permanently, and to be able to replace heart transplantation in the future.

Equipment Design↗

PubMedDate not supplied

How to produce a pulsatile flow with low haemolysis?

It is evident that a pulsatile flow is important for blood circulation because the flow pulsatility can reduce the resistance of peripheral vessels. It is difficult, however, to produce a pulsatile flow with an impeller pump, since blood damage will occur when a pulsatile flow is produced. Further investigation has revealed that the main factor for blood damage is turbulence shear, which tears the membranes of red blood cells, resulting in free release of haemoglobin into the plasma, and consequently leads to haemolysis. Therefore, the question for developing a pulsatile impeller blood pump is: how to produce a pulsatile flow with low haemolysis? The authors have successively developed a pulsatile axial pump and a pulsatile centrifugal pump. In the pulsatile axial pump, the impeller reciprocates axially and rotates simultaneously. The reciprocation is driven by a pneumatic device and the rotation by a dc motor. For a pressure of 40 mm Hg pulsatility, about 50 mm axial reciprocating amplitude of the impeller is desirable. In order to reduce the axial amplitude, the pump inlet and the impeller both have cone-shaped heads, and the gap between the impeller and the inlet pipe changes by only 2 mm, that is the impeller reciprocates up to 2 mm and a pressure pulsatility of 40 mm Hg can be produced. As the impeller rotates with a constant speed, low turbulence in the pump may be expected. In the centrifugal pulsatile pump, the impeller changes its rotating speed periodically; the turbulence is reduced by designing an impeller with twisted vanes which enable the blood flow to change its direction rather than its magnitude during the periodic change of the rotating speed. In this way, a pulsatile flow is produced and the turbulence is minimized. Compared to the axial pulsatile pump, the centrifugal pulsatile pump needs only one driver and thus has more application possibilities. The centrifugal pulsatile pump has been used in animal experiments. The pump assisted the circulation of calves for several months without harm to the blood elements and the organ functions of the experimental animal. The experiments demonstrated that the pulsatile impeller pump is the most efficient pump for assisting heart recovery, because it can produce a pulsatile flow like a diaphragm pump and has no back flow as occurs in a non-pulsatile rotary pump; the former reduces the circulatory resistance and the latter increases the diastole pressure in aorta and thus increases the perfusion of coronary arteries of the natural heart.

Animals↗

PubMedDate not supplied

Permanent magnetic-levitation of rotating impeller: a decisive breakthrough in the centrifugal pump.

Magnetic bearings have no mechanical contact between the rotor and stator, and a rotary pump with magnetic bearings therefore has no mechanical wear and thrombosis. The magnetic bearings available, however, contain electromagnets, are complicated to control and have high energy consumption. Therefore, it is difficult to apply an electromagnetic bearing to a rotary pump without disturbing its simplicity, reliability and ability to be implanted. The authors have developed a levitated impeller pump using only permanent magnets. The rotor is supported by permanent radial magnetic forces. The impeller is fixed on one side of the rotor; on the other side the rotor magnets are mounted. Opposite these rotor magents, a driving magnet is fastened to the motor axis. Thereafter, the motor drives the rotor via magnetic coupling. In laboratory tests with saline, where the rotor is still or rotates at under 4,000 rpm, the rotor magnets have one point in contact axially with a spacer between the rotor magnets and the driving magnets. The contacting point is located in the center of the rotor. As the rotating speed increases gradually to more than 4000 rpm, the rotor will disaffiliate from the stator axially, and become fully levitated. Since the axial levitation is produced by hydraulic force and the rotor magnets have a giro-effect, the rotor rotates very stably during levitation. As a left ventricular assist device, the pump works in a rotating speed range of 5,000-8,000 rpm, and the levitation of the impeller is assured by use of the pump. The permanent maglev impeller pump retains the advantages of the rotary pump but overcomes the disadvantages of the leviated pump with electromagnetic-bearing, and has met with most requirements of artificial heart blood pumps, thus promising to have more applications than previously.

Equipment Design↗

PubMedDate not supplied

Technical note: a durable impeller pump with rolling bearing and purge system.

Our former works demonstrated that the authors' impeller pump could support the circulation of experimental animals for several months without harm to blood elements and organ function of the animals. The termination of the experiments was mostly related to wear of the mechanical bearing and the thrombosis along the bearing. To solve the bearing problem, a magnetic bearing was investigated in our laboratory, resulting in some new problems, such as complicated design and control, considerable energy consumption and lower reliability. Progress in developing an impeller pump for long-term application has been achieved recently. Instead of using a slide bearing, a rolling bearing system has been devised. Its service life is more than ten years due to a wear-proof roller made of ultra-high molecular weight poythene. In order to avoid thrombus formation, a special purge system was introduced to the bearing, thus saline with heparin can be infused through the bearing into the pump. Therefore, the bearing keeps working in the saline, and no thrombus will be formed along the beating. The animal experiments demonstrated that 30 cc fluid infusion per hour continuously or interruptedly is enough to prevent the thrombus formation. With these improvements, the impeller pump was continuously run for one year and no bearing wear was measured in the endurance test. The device weighing 150g is fully implantable, consumes around 9.6 W electric energy by delivering 9 l min(-1) blood flow against 120 mmHg mean pressure and reaches a highest total efficiency, 24.7%, of motor (including controller) and pump at this point, which can produce both pulsatile and non-pulsatile flow according to the requirements.

Animals↗

PubMedDate not supplied

Streamlined design of impeller and its effect on pump haemolysis.

To investigate the effect of impeller design on pump haemolysis, five impellers with different numbers of vanes or different vane angles were manufactured and tested in one pump for haemolysis comparison. The impellers had the same dimension and logarithmic spiral vane form that coincided with the stream surfaces in the pump, according to an analytical and three-dimensional design method developed by the authors. Consequently, an impeller with six vanes and a 30 degrees vane angle had the lowest haemolysis index. The result agrees with the theoretical analyses of other investigators searching for the optimal vane number and vane angle to achieve the highest efficiency of the pump.

Biomedical Engineering↗

PubMedDate not supplied

Experimental method to reveal the effect of rotor magnet size and air gap on artificial heart driving motor torque and efficiency.

To investigate experimentally the effect of rotor magnet design on artificial heart driving motor performance, seven rotors with different magnet lengths or thicknesses, as well as different peripheral angles, were manufactured and tested in the same motor stator with different rotating speeds. The input power (voltage and current) and output torque were measured and the motor efficiency was computed. The results demonstrated that the reduction of rotor magnet size and the enlargement of the air gap between the rotor magnets and the stator coil core have no significant effect on motor efficiency, but will reduce the torque value on which the motor achieves the highest efficiency; it could be remedied however by increasing the rotating speed, because the torque at the high efficiency point will increase along with the rotating speed. These results may provide a basis for developing small rotor magnets, large air gap and high efficiency motors for driving an artificial heart pump.

Air↗

PubMedDate not supplied

A novel impeller TAH using magnetic bearings for load reduction.

A novel impeller TAH (total artificial heart), i.e. bi-ventricular assist impeller pumps, has been developed. The device consists of a rotor with motor magnets and two impellers, a stator with motor coil and iron core, and two pump housings. In both sides of the rotor magnets, as well as the stator coil core, a pair of magnetic bearings was devised to partly counteract the attractive forces between the rotor magnets and the stator coil core. This means the magnetic bearings are used for load reduction. On hydrodynamic testing, the two pumps both produced a flow rate as high as 6 l min(-1) and the left pump had a pressure head of 150 mm Hg, and that of the right pump was 50 mm Hg. The highest efficiency of the device, including the motor, the two pumps and the controller, reached 14.7%. The device, weighing 250 g, had a length of 80 mm and a diameter of 40 mm at its largest point. Currently in the world, this is a unique TAH, which is electrically powered and driven by a single motor and has only one moving part, can produce either pulsatile or non-pulsatile flow, both pumps eject flow synchronistically by pulsatile mode, and the volume equilibrium of the two pumps can be achieved automatically without the need for control.

Equipment Design↗

PubMedDate not supplied

Toward a durable impeller pump with mechanical bearings.

Our former work demonstrated that our impeller pump could support the circulation of experimental animals for several months without harm to blood elements or organ function. The termination of the experiments was mostly related to wear of the mechanical bearing and thrombosis along the bearing. To solve the bearing problem, we investigated a magnetic bearing in our lab, which resulted in some new problems, such as complicated design and control, considerable energy consumption, and lesser reliability. Progress in developing an impeller pump for long-term application has recently been achieved. Instead of using a sliding bearing system, we devised a rolling bearing system. Its service life is more than 10 years because of a wearproof roller made of ultra high molecular weight polythene. To avoid thrombus formation, we introduced a special purge system to the bearing, allowing the saline with heparin to be infused through the bearing into the pump. The bearing, therefore, keeps working in the saline, and no thrombus will be formed. Animal experiments demonstrated that a 30 ml fluid infusion per hour is enough to prevent thrombus formation. With these improvements, the impeller pump has continuously run for 8 months, and no bearing wear can be measured. The device, weighing 150 g, is fully implantable, consumes approximately 9.6 watts, and delivers a 9L/min blood flow against a 120 mm Hg mean pressure and reaches a highest total efficiency of 24.7% for the motor (including the controller) and pump. The system can produce both pulsatile and nonpulsatile flow according to requirements.

Animals↗

PubMedDate not supplied

Axial reciprocation of rotating impeller: a novel approach to preventing thrombosis in centrifugal pump.

For long-term application, rotary pumps have to solve the problems of bearing wear and thrombosis along the bearing. Some investigators choose the magnetic bearing for zero friction and to provide no contact between the rotor and stator; the former avoids the mechanical wear and the latter eliminates the possibility of thrombus formation. The authors have tried and have found, however, that it is difficult to apply a magnetic bearing to the rotary pump without disturbing its simplicity, reliability, and implantability, and have therefore developed a much simpler approach to achieve the same results. Instead of using a sliding bearing, a rolling bearing has been devised, and its friction is about 1/15 that of the sliding bearing. Furthermore, a wearproof material of ultra high molecular weight polythene has been adopted to make the rollers, and its antiwear property is eight times better than metal. The service life of the bearing has thus been prolonged. To prevent thrombus formation along the bearing, the impeller reciprocates axially as the impeller changes its rotating speed periodically to produce a pulsatile flow. The reciprocation is the result of the effects of a magnetic force between the motor rotor and stator and a hydraulic force between the blood flow and the impeller. Similar to a piston pump, the oscillating impeller can make the blood flow in and out of the bearing, resulting in washout with fresh blood once a cycle. This obviously helps to prevent thrombosis along the bearing and in the pump. Endurance tests with saline of this novel pump demonstrated device durability, promising long-term assisted circulation.

Centrifugation↗