ABSTRACT
The analysis of pathological electrocardiogram (ECG) signals is of importance for aided clinical diagnosis. We analyzed the self-similarity of normal heart rhythm, congestive heart failure and sudden cardiac death signal in the present paper using detrended fluctuation analysis (DFA), in order to achieve these two pathological ECG signal detection. The scale index(alpha) was achieved by analyzing and detecting normal heart rhythm, congestive heart failure and sudden cardiac death in the MIT-BIH standard database. Analysis of variance showed that the scale index could distinguish between congestive heart failure and sudden cardiac death accordingly.
Subject(s)
Humans , Death, Sudden, Cardiac , Electrocardiography , Methods , Fractals , Heart Failure , Nonlinear Dynamics , Signal Processing, Computer-AssistedABSTRACT
Time irreversibility is a fundamental property of nonequilibrium systems. It is significant to measure the trend of change of time irreversible index under different physiological and pathological state of electrocardiosignal. We analyzed and tested the heart rate variability (HRV) signals of the normal sinus rhythm, atrial contraction, sinus bradycardia in the MIT-BIH standard database using the multiscale time irreversiblity method. It was shown that the time irreversiblity index of the normal heart rhythm, atrial premature beats and bradycardia were in the decreasing trend. The results would be helpful to clinical diagnosis as a secondary means.
Subject(s)
Humans , Arrhythmia, Sinus , Atrial Premature Complexes , Bradycardia , Electrocardiography , Methods , Heart Rate , Physiology , Signal Processing, Computer-Assisted , Time FactorsABSTRACT
OBJECTIVE:To prepare diclofenac sodium controlled release tablet,and to evaluate the mechanism of drug release.METHODS:Stearic acid and ethyl cellulose were used as blocking agents and sodium carboxylmethyl starch was used as disintegrating agent.Tablets were made after drying the granules prepared.The dissolution rates were acquired according to Chinese Pharmacopoeia(1995).RESULTS:Drug release from the tablets prepared was of zero-order release before 90% of drug released.No significant influences were observed from the dissolution rates of the different pressure of tablet(5～10kg),amount of drugs contained in the tablet(35%～60%)and different geometry of the tablets,respectively.The remarkable difference waw observed between the disintegrating and blocking agents contained in the tablets.CONCLUSION:The time of 50% of durg released could be changed as the amount of disintegrating or blocking agents were changed.
ABSTRACT
Objective To develop and charaterize a series of Poloxamer-and Carbopol-based in situ gel for ophthalmic use as to enhance the ability of drug to retain in eyes and delay drug release.Methods The gel was prepared using Poloxamer 407/188 and Carbopol 974P as gelling agent and viscosity enhancer,respectively.Rheological characteristics were evaluated and behaviour of drug release in vitro was investigated by modified Franz diffusion cells.Results The rheological study indicated that the gel was physically entangled polymer solutions at 20 ℃ and then converted into a network structure with secondary bonds at 35 ℃.The gel released the drug molecules slowly in 4 h.The best fit model was Higuchi matrix model(r=0.992 3).Formulations consisting of Poloxamer 188 and Carbopol 974P were proved to be able to decrease the drug release speed efficiently.The impact on elastic modulus G" of the gel caused by those two were different.Conclusion An in situ gel with suitable sol-gel transition temperature and satisfactory release pattern could be achieved by adjusting the ratio of Poloxamer 407 to Poloxamer 188.The developed formulations have the ability to prolong the ocular residence time,which suggests it may be a new durg delivery system with bright future.
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Objective To investigate the effect of lipid emulsion as drug carrier on pancreas targeting capability of hydroxycamptothecin. Methods Hydroxycamptothecin-loaded lipid emulsion was prepared by a two-step emulsifying process with soybean phospholipid and soybean oil as main excipients. Hydroxycamptothecin-loaded lipid emulsion and hydroxycamtothecin injection were iv administrated to rabbits at a single dose of 3.5 mg/kg. The hydroxycamptothecin concentration in the pancreas was determined by HPLC with camptothecin as the internal standard. Results The HPLC method for the determination of hydroxycamptothecin and camptothecin was sensitive and accurate. The hydroxycamptothecin concentration in the pancreas was greatly improved in hydroxycamptothecin-loaded lipid emusion compared with hydroxycamtothecin injection. Conclusion The pancreatic gland targeting capability is greatly improved, when lipid emulsion is used as drug carrier.
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Objective To prepare stable silybin oral microemulsion. Methods The formulation of the silybin oral microemulsion was optimized by the combination of surface tension measure, pseudo-ternary phase diagram drawing and orthogonal design. Results Microemulsion type was identified. Average particle diameter was measured. Distribution of silybin in microemulsion was measured by ultracentrifugation. The centrifugalization and influencing factors experiment of microemulsion were carried out,which could keep homogeneous and stable for three months on the storage condition of room temperature. Meanwhile,the influence of high-temperature and illumination was a little. Conclusion Stable oral microemulsion silybin can be prepared in this formulation, with fine-looking and desirable stability which is better for the further studies.