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Biomedical subjects

B Erdélyi

Publications and source records attributed to B Erdélyi.

9 recordsLinked to original sources
PubMed2001

Optimal symplectic approximation of Hamiltonian flows.

Long term simulations of Hamiltonian dynamical systems benefit from enforcing the symplectic symmetry. One of the several available methods to perform this symplectification is provided by the recently developed theory of extended generating functions. The theory offers an infinite supply of generator types that can be used for symplectification. Using Hofer's metric, a condition for optimal symplectification is given. In the weakly nonlinear case, the condition provides a generator type that, based on the limited information available on the system, in general gives optimal results.

Journal Article↗
PubMed2001

Corneal topography changes after a 15 second pause in blinking.

PURPOSE: To examine the effect of a short pause in blinking on the quantitative topographic parameters of the corneal surface. SETTING: Refractive corneal surgery unit of a university eye hospital. METHODS: Using a TMS-1 instrument (Computed Anatomy, Inc.), corneal topographic parameters were measured 5 and 15 seconds after a complete blink in 12 healthy subjects. The main outcome measures were changes in the surface regularity index (SRI) and the surface asymmetry index (SAI). RESULTS: During the pause in blinking, the mean SRI value increased from 0.18 +/- 0.19 (SD) to 0.30 +/- 0.19 (P <.02) and the SAI from 0.21 +/- 0.08 to 0.24 +/- 0.10 (P =.079, not statistically significant). There were no significant changes in the values for potential visual acuity, corneal refractive power, or astigmatism. CONCLUSION: The results indicated a significant change in corneal topography during even a short pause in blinking. In follow-up studies using corneal topography, all measurements should be done at a fixed time after a complete blink.

Adult↗
PubMed1993

[The place of percutaneous transluminal angioplasty in the management of obliterative vascular diseases of the lower extremities. Femoro-popliteal arterial angioplasty].

Authors treated 331 patients having symptoms of femoropopliteal stenoses or occlusions with transluminal angioplasty from 1983. They performed 186 dilatations and 189 recanalizations. Procedures were preceded by medicinal preparation. The primary technical success rate was 94.6% after dilatation, and 79.9% after recanalisation. In case of stenosis the success rate did not show significant connection with the length of the dilated segment but in case of occlusion longer than 6 cm the success rate decreased. After procedure 87.2% of the patients became asymptomatic, or improved. 21 (5.6%) complications (7 inguinal hematomas, 6 emboles, 6 thromboses, one perforation of arterial wall) occurred and twelve of them required surgical intervention. One patient died after angioplasty due to cardiac failure. Authors are of the opinion that femoropopliteal occlusions and stenoses shorter than 6 cm should be treated by angioplasty. They suggest making balloon catheter dilatation for multiple stenoses even they are longer than 6 cm.

Aged↗
PubMed1992

[Pseudoaneurysm in a pancreatic pseudocyst].

Four cases with pseudoaneurysm developed on the basis of pancreatic pseudocyst are reported. Regarding data obtained from literature diagnostic and therapeutic possibilities and their success rates are analysed. Authors summarize both specific and non-specific signs of the pancreatic pseudoaneurysm obtained from duplex scan. All of their patients were successfully treated by operation. They call attention to the benefit of the selective feeding artery ligature. Importance of ultrasound follow up of patients suffering from pancreatitis is pointed out, as a prevention of the massive hemorrhage which is the most serious complication of the pancreatic pseudoaneurysm.

Alcoholism↗
PubMed1992

[The place of percutaneous transluminal angioplasty in the treatment of obliterative vascular diseases of the lower limbs. Angioplasty of of the iliac system].

Between 1983-91 386 patients with hemodinamically significant stenosis or short-segment occlusion of iliac arteries were treated by transluminal angioplasty. 487 dilatations and 13 recanalizations were performed. In 353 (70.2%) of these cases were carried out without medicinal preparation continuously after the diagnostic angiography. The technical success rate was 93.4%. The technical success rate did not depend on medicinal preparation. 93% of their patients became symptomless or improved. 28 complications were noted (7 thrombosis, 4 embolisms, 14 inguinal haematomas, 2 false aneurysms, 1 bleeding), 11 of them required surgical intervention. One patient died because of cardiac failure due to retroperitoneal haematoma. Authors' opinion isolated short uni- and bilateral iliacal stenosis can be treated by transluminal angioplasty. Longer or multifocal stenosis required individual consideration.

Aneurysm↗
PubMedDate not supplied

Reproducibility of keratometric measurements decreases with time after blinking.

PURPOSE: The reproducibility of keratometry measurements was investigated in relation to the elapsed time after blinking. METHODS: Thirty ophthalmologically healthy subjects were examined, using a standard corneal topographic instrument (17 women, 13 men, age 25.7+/-5.6 years). Photographs were taken in series of four: at 5, 15, 30, and 60 seconds after a complete blink. The series was repeated three times in each individual. The main outcome measures were the mean values, the standard deviation, and the reproducibility error of the simulated keratometric values (K1, K2), the surface regularity index (SRI), and the surface asymmetry index (SAI). RESULTS: The mean of K 1 and K 2 values did not change (p=0.684 and p=0.982); however, the measurement error increased significantly for K1 (p=0.007) and for K2 (p=0.038). The mean values of SRI changed significantly (p=0.034) during the 1-minute pause in blinking together with a non-significant change in the standard deviation (p=0.106), without elevation of the measurement error (p=0.619). The elevation of SAI with time was not significant (p=0.093). CONCLUSIONS: The break-up phenomenon of the tear film at the ocular surface induces significant deterioration of the reliability of keratometric measurements on prolonged gaze without blinking. The created error can exceed 0.6 D, which is unacceptably high in practice. Therefore care should be taken to avoid such circumstances during the examination.

Adult↗