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Biomedical subjects

B Duan

Publications and source records attributed to B Duan.

12 recordsLinked to original sources
PubMed1999

[The development of a hemorrhologity observating and measuring instrument].

A new instrument for observing blood cell state and the process of variation on hemorrheology has been developed. There are three ways of shear rate: setting by hand, automatically setting and simulating pulsative state. It can provide different variable flow fields. The shear rate can be set in the range from 0.1 to 1000 s-1. It needs only a little blood. It can be easyly and rapidely operated. it has clear images. The hemorrheology state of blood cells can be directly perceived through thd instrument by eyes. The display and measurement and record of blood cell's hemorrheology state can be finished in real time dynamically and simultaneously.

Equipment Design↗
PubMed1997

[The development of a multifunction shear flow field generating device].

A new shear flow field generating device has been developed. It can be widely used in the basic research of hemorheology, clinical test and measurement. It has rich functions and can make dynamic measurement of hemorheology parameters. There are three work ways of shear rate: setting by hand, automatically setting and simulating pulsative state. It can provide different variable flow fields. The shear rate can be set in the range from 0.1 to 1000 s-1.

Equipment Design↗
PubMed1995

Mechanics of wave reflections in a coronary bypass loop model: the possibility of partial flow cut-off.

Local hemodynamics in a bypass loop model with dimensions typical of those in the human coronary circulation are studied, particularly with regards to the effects of wave reflections. While in a single vessel of such dimensions and a single source of wave reflections the effects would be insignificant, in a bypass loop the combination of a narrowed vessel with a converging junction and several reflection sites may produce wave reflections with significant effects on the pressure and flow distributions within the vessels forming the loop. Calculations to test this possibility were performed, based on D'Alembert's solutions of the wave equation and with a proposed matching scheme to deal with the converging junction. The results indicate that there are very large wave reflection effects at a frequency of 10 Hz, smaller but significant effects at 5 Hz, and some insignificant effects at 1 Hz. The results also indicate that partial flow cut-off may occur within the loop under some singular circumstances, whereby certain harmonic components of the incident wave are totally reflected. In the clinical setting these effects would detract from the efficiency of the bypass as a conduit, to a degree dependent on the degree of occlusion of the bypassed vessel. The choice of a larger diameter for the bypass appears to diminish this dependence and is thus on the whole favorable despite the contribution it makes to impedance mismatch at the junction.

Biomechanical Phenomena↗
PubMed1993

Reflection coefficients in pulsatile flow through converging junctions and the pressure distribution in a simple loop.

Analytical expressions for the reflection coefficients in pulsatile flow through converging junctions are derived by two independent methods and are used to study the effects of wave reflections on the pressure distribution in a simple vascular loop. A simulated physiological situation is used as an example in which the loop is formed by the combination of a bypass and a bypassed vessel, the relative diameter of the latter being varied in order to simulate a narrowing. The results demonstrate how, in the case of a converging junction, the effects of wave reflections on the pressure distribution in one vessel depend on conditions within the vessel itself as well as in the other. The new reflection coefficients take into account this interdependence of flow in the two vessels forming a converging junction, and are shown to be consistent with reflection coefficients commonly used in diverging junctions.

Aorta, Abdominal↗
PubMed1993

[The analysis of human DNA fingerprints by the synthetic oligonucleotide probe].

In order to test the practical applicability of oligonucleotide fingerprinting we have investigated 50 unrelated individuals, 11 members in two families and one pair of twin using the probe (CAC)5/(GTG)5. Except the monozygotic twins highly variable patterns were demonstrated, even in a family. The probability of chance association between random individuals was calculated as 3.8 x 10(-10). It seems reasonable to conclude that (CAC)5/(GTG)5 fingerprints are completely individual-specific. The results of the pedigree study showed that the inheritance of alleles was in keeping with the Mendelian Law. This method is not so costly and labor-intensive as the conventional Southern blotting. It increases the speed and lessen the complexity of RFLPs study.

DNA Fingerprinting↗
PubMed1993

[An evaluation of DNA fingerprinting with oligonucleotide probe for forensic purposes].

The synthetic oligonucleotide probe (CAC)5/(GTG)5 for DNA, fingerprinting was studied in this paper. The incomplete pattern of DNA fingerprints was obtained from bloodstains up to three years old, which were kept at room temperature. The identical results were achieved from various human organ tissues of the same individual. DNA fingerprints from vaginal swabs was the same as that obtained from the male donor's blood. The discernible DNA fingerprints were obtained with as little as 250ng of genomic DNA. Besides, using restriction enzyme Hae III instead of Hinf I to digest human DNA, the highly polymorphic hybridization pattern was also obtained. A practical case was tested by Hinf I and Hae III digestion, respectively. The results demonstrated that the (CAC)5/(GTG)5 was a suitable probe for DNA fingerprinting in forensic practice.

Base Sequence↗
PubMed1991

Secondary prevention of myocardial reinfarction with low dose aspirin.

A clinical trial of secondary prevention of reinfarction with low dose aspirin is reported. 50 mg aspirin per day was administered in 216 case. 211 cases did not take aspirin or any other antiplatelet agents as a control group. The follow-up periods in the two groups were 19.4 +/- 12.6 mon and 20.7 +/- 13.0 mon, respectively. There were 175 males in the aspirin group and 137 males in the control group. The incidence of reinfarction was reduced by 65% and platelet aggregation was inhibited obviously in the aspirin group as compared to the control group in men, whereas no significant trends were observed in women.

Aged↗
PubMedDate not supplied

Pressure peaking in pulsatile flow through arterial tree structures.

An analytical iterative scheme is presented for computing the local characteristics of pressure and flow waves as they progress along a tree structure and become modified by wave reflections. Results are obtained to illustrate the phenomenon of pressure peaking under two different sets of circumstances. In the first case, the propagation of a single harmonic wave along a simple tree is considered, where wave reflections modify the amplitude of the pressure wave as it travels. In the second case, the propagation of a composite wave along a tree with multiple branches is considered, where wave reflections modify the shape of the wave as it travels and cause it to peak. The results demonstrate unambiguously that the root cause of this phenomenon is wave reflections caused by stepwise decreases in admittance, as has been previously suggested, rather than due to nonlinear interactions, as has also been previously suggested. It is shown clearly that even when wave reflections combine linearly, they lead to considerable peaking in the pressure waveform.

Animals↗
PubMedDate not supplied

[Multi-locus DNA fingerprints using oligonucleotide probe (CAC)5/(GTG)5 in the Chinese population].

In order to test the practical applicability of oligonucleotide fingerprinting in China we have investigated unrelated individuals, family members and a pair of twins from the Beijing area using the probe (CAC)5/(GTG)5. Except for the monozygotic twins highly variable banding patterns were demonstrated as expected for the randomly selected individuals but also for the relatives. On the basis of an initial survey of 50 unrelated individuals the calculated probability for obtaining by chance two identical multilocus patterns is very small (less than 1.93 x 10(-13). Therefore it seems reasonable to conclude that like in caucasians, (CAC)5/(GTG)5 fingerprints are completely individual-specific also in this population. Therefore they have already been used successfully for identification purposes and paternity tests in many actual cases.

China↗