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Biomedical subjects

P Dressler

Publications and source records attributed to P Dressler.

11 recordsLinked to original sources
PubMed2006

Fluorescence X-ray absorption spectroscopy using a Ge pixel array detector: application to high-temperature superconducting thin-film single crystals.

A Ge pixel array detector with 100 segments was applied to fluorescence X-ray absorption spectroscopy, probing the local structure of high-temperature superconducting thin-film single crystals (100 nm in thickness). Independent monitoring of pixel signals allows real-time inspection of artifacts owing to substrate diffractions. By optimizing the grazing-incidence angle theta and adjusting the azimuthal angle phi, smooth extended X-ray absorption fine structure (EXAFS) oscillations were obtained for strained (La,Sr)2CuO4 thin-film single crystals grown by molecular beam epitaxy. The results of EXAFS data analysis show that the local structure (CuO6 octahedron) in (La,Sr)2CuO4 thin films grown on LaSrAlO4 and SrTiO3 substrates is uniaxially distorted changing the tetragonality by approximately 5 x 10(-3) in accordance with the crystallographic lattice mismatch. It is demonstrated that the local structure of thin-film single crystals can be probed with high accuracy at low temperature without interference from substrates.

Algorithms↗
PubMed2006

[Morphology, family history, and age at diagnosis of 26 patients with Axenfeld-Rieger syndrome and glaucoma or ocular hypertension].

PURPOSE: The Axenfeld-Rieger syndrome (ARS) shows genetic and morphologic heterogeneity and is associated with glaucoma in 50% of the patients. METHODS: Ocular, dental, and systemic anomalies, maximum intraocular pressure (IOPmax), frequency of ARS or glaucoma in the family history (FH), and age at diagnosis (AAD) of 26 consecutively examined patients with ARS and glaucoma or elevated IOP were evaluated retrospectively. RESULTS: In 65.4% of the patients hypoplasia of the iris was found. Almost 50% of the patients had systemic anomalies, dental anomalies being the most frequent. Of 26 patients, 12 (46.2%) had an ARS in the FH; 57.7% of the patients had a FH of glaucoma with or without ARS. No significant differences in IOPmax and frequency of iris hypoplasia and glaucoma surgery were found when patients with and without ARS in their FH and patients with and without iris hypoplasia were compared. CONCLUSION: Patients with iris hypoplasia and patients with ARS and/or glaucoma in the FH do not show a worse glaucoma prognosis than patients without iris hypoplasia or without a FH of glaucoma or ARS. ARS was diagnosed within the 1st year of life in approximately half of the patients. Therefore, children of ARS patients should be screened as soon as possible to improve early diagnosis of ARS and glaucoma and to improve glaucoma prognosis. As the dental and facial anomalies may require treatment in the first dentition, patients with ARS should be referred to a dentist or orthodontist.

Abnormalities, Multiple↗
PubMed2004

Advanced detection systems for X-ray fluorescence excitation spectroscopy.

This paper accounts for selected detector developments carried out over the past 15 years within the ESRF X-ray Absorption Spectroscopy group. This includes various types of photodiodes used as integrated current detectors. Special emphasis is put on the long-standing development of a Si drift-diode array suitable for energy-dispersive detection of X-ray fluorescence. This detector, which is now operational, was used to record high-quality XMCD/XAFS spectra on [Fe70Pt30] nanoparticles highly dispersed on a Si wafer. Using numerically deconvoluted spectra, energy resolution was decreased to 82 eV for the Si Kalphabeta line, 126 eV for the Fe Kalpha line and 176 eV for the Pt Lalpha line. A high-vacuum-compatible high-energy-resolution crystal analyzer was also installed on ID12, making it possible to record X-ray fluorescence excitation spectra in the photon-in/photon-out mode over a wide spectral range. Prospects of adapting these methods in order to investigate biological samples are briefly discussed.

Equipment Design↗
PubMed2002

[Separation of the airways: historical aspects].

Techniques to separate the airways to both lungs were employed in the laboratory by renowned physiologists like Pflüger and C. Bernard to study gas exchange. Pflüger's catheter, as used by Wolffberg in 1871 in the dog, essentially constituted an early example of endobronchial single lumen tube, and was to be the first airway separator introduced into man by Loewy and v. Schrötter in 1905 in experiments on circulation. As a variation of this device the carinal hook made ist appearance used by Hess in 1912 in rabbits. While the endobronchial catheters afforded airtight access to only one lung at a time for concomitantly studying ventilation in both lungs, a short tracheal cannula was combined with one introduced into the left main bronchus by Head in 1889, constituting as it were the prototype of double lumen (DL) tubes applicable to rabbits and turtles even. Werigo described 1892 a coaxial DL-tracheostomy cannula for dogs which construction principle was adopted in the first DL-bronchoscope used in man. In lung surgery during the 30s and 40s the ventilated lung was prevented from drowning by pus or secretions from the lung under surgery by sealing off ist main bronchus, either by endobronchial intubation or by a bronchial blocker inserted alongside the endotracheal tube. This principle gave rise to sophisticated devices, from the fixed combination of tube and blocker to the present-day tube housing a movable blocker. Remarkably, DL-intubation in its proper sense then was performed in bronchospirometry only. This technique was introduced by Jacobaeus upon suggestion of Liljestrand when dissatisfied with the restriction to sequential spirometry by customary bronchoscopic catheterization, relying on Frenckner's ingenious DL-bronchoscope. Rubber DL-tubes were developed by Gebauer 1939 and Zavod 1940 exclusively with bronchospirometry in mind, even E. Carlens primarily constructed his tube to improve this procedure. After its usage in over 100 bronchospirometries it was introduced for the first time in November 1949 for its familiar purpose: the resection of a tuberculous abscess in the right upper lobe. Once introduced into thoracic anaesthesia, the DL-principle so far fostered a wide variety of tube designs.

Animals↗
PubMed1998

Development of 32-channel silicon drift detectors and digital electronics for X-ray spectroscopy.

The performance of silicon-drift-detector (SDD) arrays and digital electronics designed for X-ray absorption spectroscopy in the fluorescence excitation mode is reported. Different detectors have been manufactured and tested: two single-channel SDDs with different active areas (10 mm(2) and 1 cm(2)) and a monolithic 2 cm(2) SDD with eight readout anodes. The energy resolution varies between 160 and 170 eV FWHM. A new digital multichannel shaping amplifier has been produced. Its performance is presented in comparison with that of a standard commercial shaper.

Journal Article↗
PubMed1986

[The history of anesthesia at the Heidelberg University].

An account is given on the development of general anaesthesia at the university clinics of Heidelberg. During the last century mainly chloroform was employed for general anaesthesia. Important events were the first demonstration of Koller's local anaesthesia in the eye in 1884, the first intubation for anaesthesia in Heidelberg, performed by F. Kuhn of Kassel and the development by M. Neu of a rotameter apparatus for nitrous oxide/oxygen anaesthesia in 1910. From 1932 on the surgeon M. Kirschner advanced the methods of high pressure infiltration for regional anaesthesia and segmental hypobaric spinal anaesthesia. In 1951 K. H. Bauer requested R. Frey to set up an "anaesthesia squad" consisting of 2 physicians and 3 nurses to become the nucleus of today's Institute of Anaesthesiology, with O. H. Just as its first professor and chairman.

Anesthesia↗
PubMed1982

[Combined use of dihydralazine and nitroglycerin during and after cardiac surgery (author's transl)].

The haemodynamic effect of combined intravenous administration of 18 mg/h dihydralazine and 0.6 mg/h nitroglycerine was examined in the intraoperative and postoperative phases of cardiac surgery (replacement of the aortic and mitral valve or of both valves, and aortocoronary bypass surgery(. Indication for therapy was supplied by a preoperative cardiac index below 2.8 l/min . m2 and an enhanced peripheral resistance above 1200 dyne . sec . cm-5. During a 19-hour observation period the haemodynamic parameters such as cardiac index (+36%) and stroke index (+19%) increased significantly within the investigated group, whereas the peripheral vascular resistance dropped by 16% and the left atrial pressure by 20%. Arterial mean pressure and heart rate did not change. In a patient group treated exclusively with nitroglycerin, the cardiac index decreased (-8%), while the peripheral vascular resistance increased (+6%); an untreated control group showed an increase of the cardiac index by 5%, whereas there was no appreciable change in peripheral vascular resistance and stroke index. The combined use of dihydralazine and nitroglycerin during the perioperative phase of cardiac surgery appears recommendable, since it is possible by such administration to monitor cardiac preload and afterload due to selectivity of the pharmacological sites of action.

Adult↗
PubMed1981

Experimental studies on microcirculation under normobaric hyperoxia using the microspheres method.

The perfusion of the heart, kidneys, adrenals, stomach, intestines, brain and musculature under normobaric hyperoxia was studied in anaesthetized mini pigs using radioactively labelled microspheres. After a 2-hour control period using room air, the influence of normobaric hyperoxia on the perfusion of the organs was measured at 2-hour intervals. A significant increase in the perfusion of tissue was found in the kidneys, adrenals, gastro-intestinal tract and brain after 4-6 hours of exposure. No change in perfusion could be demonstrated for the myocardium. Values for the skeletal musculature (diaphragm and musculus psoas) were widely scattered, but an increase could be suspected. The increase in tissue perfusion at constant blood pressure and pulse rate must be interpreted as an expression of vasodilation. These results are contrary to the majority of statements in the literature, which mainly report vasoconstriction under normobaric hyperoxia.

Adrenal Glands↗
PubMed1979

[Studies of gastric circulation in the dog, II. Ligation of main arteries (author's transl)].

Following ligation of a single gastric artery total and regional gastric blood flows are measured using radioactive microspheres of 8 mu size. There is no significant influence on total gastric blood flow. Within the depending anatomical region no significant reduction of total wall blood flow can be determined. However, blood flow to the antrum mucosa is reduced to approximately 40% after ligation of any gastric artery. Thus, it can be concluded that ligation or embolisation of a single gastric artery in diffuse gastric bleeding does not necessarily reduce or terminate the bleeding.

Animals↗
PubMed1978

[Puncture of central veins venesection in childhood (author's transl)].

Due to advances in parenteral feeding the indications for creating access to the central veins in infants and young children have become less strict. The technique of establishing such access by puncture of the internal jugular or subclavian vein is reviewed. Venesection is now indicated only in exceptional cases. The technique of placing a catheter into the umbilical artery or vein is described.

Age Factors↗