TY - GEN A1 - Janiak, Ch. A1 - Lange, K.C.H. A1 - Marquardt, P. A1 - Krüger, Ralph-Peter A1 - Hanselmann, R. ED - Sun, J. ED - Janiak, C. T1 - Propene and 1-hexene oligomerization with unbridged alkyl-substituted cyclopentadienyl- and phospholyl-zirconium/MAO catalysts - mechanistic implications from oligomer analyses by NMR, SEC, and MALDI-TOF MS PY - 2001 SP - 117 EP - 142 PB - Chemical Industry Press CY - Bejing AN - OPUS4-2193 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Reinhardt, M. A1 - Krüger, Ralph-Peter A1 - v. Lampe, I. A1 - Lorkowski, H.-J. T1 - Über Lösekinetik und Acidität einiger phenolischer Polymere T2 - 5. Berliner Polymertage 1994 CY - Potsdam DA - 1994-10-05 PY - 1994 CY - Potsdam AN - OPUS4-2199 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Wachsen, O. A1 - Krüger, Ralph-Peter A1 - Much, Helmut A1 - Schulz, Günter A1 - Reichert, K.H. T1 - Untersuchungen zur Charakterisierung des Abbaus von Polylactiden mittels 2D-HPLC und MALDI-TOF-MS T2 - Sitznung des Berliner Verband für Polymerforschung e.V. CY - Berlin DA - 1995-05-18 PY - 1995 CY - Berlin AN - OPUS4-2202 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krüger, Ralph-Peter A1 - Much, Helmut A1 - Reichert, K.H. A1 - Schulz, Günter A1 - Wachsen, O. T1 - Untersuchungen zur Charakterisierung des Polylactidabbaus mittels HPLC und MALDI-TOF-MS T2 - Präsentationsveranstaltung des Instituts für Angewandte Chemie Berlin-Adlershof e.V. CY - Berlin, Germany DA - 1995-09-26 PY - 1995 CY - Berlin AN - OPUS4-2206 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krüger, Ralph-Peter A1 - Kricheldorf, H.R. A1 - Böhme, S. T1 - Macrocycles 16. Macrocyclic Dibutyltin Dicarboxylates by Ring-Closing Polycondensation N2 - Various dibutyltin derivatives were polycondensed with aliphatic ,-dicarboxylic acids having chain lengths from 4 (succinic acid) to 22 carbon atoms. White crystalline products were obtained from all experiments, and the structure of the products was independent of the synthetic method. Viscosity measurements revealed low molecular weights (n 1 500 Da) in all cases. Vapor pressure osmometry (VPO) measurements and matrix-assisted laser desorption time-of-flight (MALDI-TOF) mass spectrometry proved that cyclic dimers and trimer were formed from dicarboxylic acids having 6 to 16 carbons, but mainly the monomeric cycle from docosane dioic acid. Heating to 250°C did not change the structure. Therefore, the results indicate that the macrocycles are the result of a thermodynamically controlled ring-closing polycondensation. This means that linear high-molecular weight poly(dibutyltin dicarboxylate)s cannot exist above room temperature. PY - 2002 DO - https://doi.org/10.1002/1521-3935(20020101)203:2<313::AID-MACP313>3.0.CO;2-V SN - 1022-1352 SN - 1521-3935 VL - 203 IS - 2 SP - 313 EP - 318 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-1796 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Krüger, Ralph-Peter A1 - Kricheldorf, H.R. A1 - Böhme, S. T1 - Macrocyclic Dibutyltin Dicarboxylates via Thermodynamically Controlled Polycondensations KW - Macrocyclics KW - MALDI KW - Oligomers KW - Polycondensation KW - Thermodynamics PY - 2002 SN - 1022-1352 SN - 1521-3935 IS - 203 SP - 313 EP - 318 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-1656 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H.R. A1 - Vakhtangishvili, L. A1 - Schwarz, G. A1 - Schulz, Günter A1 - Krüger, Ralph-Peter T1 - Macrocycles 25. Cyclic poly(ether sulfone)s derived from 4-tert-butylcatechol N2 - Poly(ether sulfone)s were prepared by polycondensation of silylated 4-tert-butylcatechol and 4,4?-difluorodiphenylsulfone in N-methylpyrrolidone. The feed ratio and the reaction time were varied to study the influence of stoichiometry and conversion on molecular weight and extent of cyclization. Molecular weights and molecular weight distributions (MWD)s were characterized by SEC measurements calibrated with polystyrene. Light scattering confirmed that calibration with polystyrene gives reasonable results and revealed a tendency towards a bimodal MWD for the samples rich in cycles. The MALDI-TOF mass spectrometry indicated that the extent of cyclization increased with higher conversion and with optimization of the stoichiometry. This interpretation was confirmed by 1H NMR endgroup analyses. For the samples with the highest molar masses only mass peaks of cycles were found, which were detectable up to 20 000 Da before and up to 27 000 Da after fractionation. Via the pseudo-high dilution method low molar mass poly(ether sulfone) containing more than 95 mol% of cycles were prepared, and even these low molar mass samples had broad MWDs. DSC measurements indicated that the glass transition temperatures depend on the structure of the endgroups and increase with higher fractions of cycles. KW - Poly(ether sulfone)s KW - Polycondensation KW - MALDI-TOF mass spectrometry PY - 2003 DO - https://doi.org/10.1016/S0032-3861(03)00410-5 SN - 0032-3861 SN - 1873-2291 VL - 44 SP - 4471 EP - 4480 PB - Springer CY - Berlin AN - OPUS4-2623 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kricheldorf, H.R. A1 - Vakhtangishvili, L. A1 - Schwarz, G. A1 - Krüger, Ralph-Peter T1 - Cyclic Hyperbranched Poly(ether ketone)s Derived from 3,5-Bis(4-fluorobenzoyl)phenol N2 - 3,5-Bis(4-fluorobenzoyl)phenol was polycondensed under various reaction conditions. Low molecular weights were obtained (Mn < 8000 Da), and MALDI-TOF mass spectrometry indicated that the chain growth was limited by cyclization. In the best mass spectra the cyclic, hyperbranched poly(ether ketone)s were detectable up to masses around 14 000 Da. When 4,4'-difluordiphenyl sulfone was added, star-shaped polymers having a diphenyl sulfone star center were formed, but cyclization was not completely suppressed. The results were compared to those obtained from "linear polycondensations" based on 4,4'-difluorobenzophenone (DFBP) and 4-tert-butylcatechol or bisphenol A. The poly(ether ketone)s of DFBP had also low molecular weights and contained high fractions of cycles. It is concluded that also in the case of hyperbranched polymers cyclization competes with propagation at any stage of the polycondensation at any concentration. Therefore, the fundamental trend of any "abn" polycondensation is the formation of star-shaped polymers having a cyclic core and hyperbranched star arms. PY - 2003 DO - https://doi.org/10.1021/ma021799x SN - 0024-9297 SN - 1520-5835 VL - 36 SP - 5551 EP - 5558 PB - American Chemical Society CY - Washington, DC AN - OPUS4-2622 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hansen, H.-C. A1 - Lagrèze, W. A1 - Krüger, Oswald A1 - Helmke, K. T1 - Dependence of the optic nerve sheath diameter on acutely applied subarachnoidal pressure - an experimental ultrasound study N2 - Purpose: To determine the distensibility and elastic characteristics of the optic nerve sheath for development of a basic understanding of ultrasound studies aimed to measure optic nerve sheath diameter (ONSD) for detection of acutely elevated intracranial pressure (ICP). Methods: Isolated human optic nerves preparations obtained from autopsies were submitted to predefined pressure alterations, and consecutive changes in ONSD were measured by B-scan ultrasound under defined conditions. Results: Following submission to pressure, the diameter of the nerve sheath increased up to 140% of its baseline value. The increase (mean 1.97 mm, SD 0.52 mm) corresponded to the magnitude of pressure steps measured in the perineural subarachnoidal space (SAS). Similarly, the ONSD declined in each of the preparations within a few minutes after the optic nerve was decompressed. However, it did not reach its baseline value again when pressure loads of 45–55 mmHg or more had been applied. Conclusions: The elasticity of the anterior sheath of the optic nerve is sufficient for the detection of pressure changes in the SAS especially for upward pressure steps. This is basically important for the application of clinical monitoring of the sheath diameter to facilitate the identification of patients with elevated ICP non-invasively (screening). However, further implementation of this procedure in neurointensive care and emergency medicine has to consider that the sheath diameter reversibility may be impaired after episodes of prolonged intracranial hypertension and a model for hysteresis is proposed. KW - Intensive care KW - Intracranial pressure KW - Neuromonitoring KW - Optic nerve sheath KW - Ultrasound PY - 2011 DO - https://doi.org/10.1111/j.1755-3768.2011.02159.x SN - 1755-375X SN - 1755-3768 VL - 89 IS - 6 SP - e528 EP - e532 PB - Blackwell CY - Oxford AN - OPUS4-24017 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gappenach, C. A1 - Krauß, H.-J. A1 - Krüger, Jörg A1 - Offenhäuser, F. A1 - Pintaske, S. T1 - Auswahl Laserschutzprodukte - eine Handreichung N2 - Wer mit Laserstrahlung zu tun hat, sollte vor allem auf den Schutz seiner Augen achten, denn die Netzhaut ist eines der empfindlichsten Gewebe des menschlichen Körpers. Auch die Hornhaut des Auges kann durch Laserstrahlung gefährdet sein. Sie hat eine Dicke von nur etwa 0,5 mm. Der Schutz der Augen vor Laserstrahlung ist durch verschiedene Maßnahmen möglich. KW - Laserschutz KW - Schutzbrille KW - Justierbrille KW - Abschirmung KW - EN 207 KW - EN 208 KW - EN 12254 PY - 2015 SN - 1432-9778 VL - 3 SP - 40 EP - 45 PB - AT-Fachverl. CY - Fellbach AN - OPUS4-33431 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -