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Bernd Schubert

Publications and source records attributed to Bernd Schubert.

4 recordsLinked to original sources
PubMed2005

A wave-packet simulation of the low-lying singlet electronic transitions of acetylene.

The vibronic structure of the S0 --> S1 and the S0 --> S2 electronic transitions of acetylene is studied theoretically based on an ab initio quantum-dynamical approach. The underlying potential-energy surfaces and transition dipole moment functions are obtained from high-level multireference calculations, including the Davidson correction. Ensuing quantum-dynamical simulations rely on the wave-packet propagation method, using grid techniques, and including three nuclear degrees of freedom (C-C stretching and both HCC bending modes for J = 0). The importance of strong anharmonicity is assessed, especially for the S2 excited state with its unusual potential-energy surface. Good overall agreement with the experimental UV absorption spectrum of acetylene is achieved in the range of 6-8 eV.

Journal Article↗
PubMed2003

Comparative prospective randomized efficacy testing of different guiding catheters for coronary sinus cannulation in heart failure patients.

INTRODUCTION: The efficacy of different shapes of guiding catheters for coronary sinus (CS) cannulation was evaluated at implant of a cardiac resynchronization therapy device that required transvenous placement of a pacing lead in a coronary vein on the left ventricle. METHODS AND RESULTS: Comparative testing of 5 different guiding catheter shapes was attempted in 29 consecutive patients. Four newer guiding catheters were tested in a prospective randomized manner with a reference standard catheter always tested in the last place. All of the new catheters included a distal shape that consisted of a single curve or a compound set of curves at the catheter tip, followed by a catheter shaft design which fell into one of two classes: (1). straight shaft catheters and (2). curved shaft catheters. The curved shaft class of catheters, two new and one standard, achieved higher (16/23 (70%), 17/23 (74%) and 17/22 (77%)) CS cannulation success rates than the straight shaft class catheters ((13/23 (56%) and 12/23 (52%)). The pairing of two catheters, one from each class in a single patient, or both from the curved shaft class resulted in a combined CS cannulation success rate of up to 96%. Two of the catheters were more effective from a left hand insertion than from a right hand insertion site. CONCLUSIONS: The ability to switch between guiding catheters with different shapes and compound curves can improve the CS cannulation success rate. The selection of guiding catheters should be influenced by the intended use of the catheter either from the left or from the right hand side.

Cardiac Catheterization↗
PubMed2002

Human experience with transvenous biventricular defibrillation using an electrode in a left ventricular vein.

This study investigated the safety and feasibility of transvenous biventricular defibrillation in ICD patients. Some patients may have high DFTs due to weak shock field intensity on the LV. Animal studies showed a LV shocking electrode dramatically lowered DFTs. This approach might benefit heart failure patients already receiving a LV lead or conventional ICD patients with high DFTs. A modified guidewire was used as a temporary left venous access defibrillation electrode (LVA lead). In 24 patients receiving an ICD, the LVA lead was advanced through a guide catheter in the coronary sinus (CS) and into a randomized LV vein (anterior or posterior) using a venogram for guidance. Paired DFT testing compared a standard right ventricular defibrillation system to a biventricular defibrillation system. There were no complications or adverse events. As randomized, LVA lead insertion success was 87% and 71% for anterior and posterior veins, respectively, and 100% after crossover. Total insertion process time included venogram time (32.5 +/- 26.9 minutes, range 5-115, mode 15 minutes) and LVA lead insertion time (15 +/- 14 minutes, range 1-51, mode 7 minutes). An apical LVA lead position was achieved in 11 (45%) of 24 patients and 7 (64 %) of these 11 displayed a DFT reduction; however, mean DFTs were not statistically different. Transvenous biventricular defibrillation is feasible and was safe under the conditions tested. Additional clinical studies are justified to determine if optimized LV lead designs, lead placement, and shock configurations can yield the same large DFT reductions as observed in animals.

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