Leibniz University of Hanover

About: Leibniz University of Hanover is a education organization based out in Hanover, Niedersachsen, Germany. It is known for research contribution in the topics: Finite element method & Population. The organization has 14283 authors who have published 29845 publications receiving 682152 citations.

Comparison of Cascaded H-Bridge and Modular Multilevel Converters for BESS application

Abstract: This paper compares the Cascaded H-Bridge (CHB) converter topology with the Modular Multilevel Converter topology (M2LC) for the use in battery energy storage systems (BESS). Standard modules are examined as well as extended modules allowing an increase in output voltage. Semiconductor and capacitor requirements are evaluated by simulation, and practical considerations are discussed. Experimental results from a laboratory setup of a CHB based BESS are presented.

Effect of intraarterial versus intravenous cisplatin in addition to systemic doxorubicin, high-dose methotrexate, and ifosfamide on histologic tumor response in osteosarcoma (study COSS-86).

Abstract: In osteosarcoma, intraarterial (IA) administration of systemic treatment has been advocated to improve local tumor response preparing for, or even obviating, definitive surgery. Because data from the literature did not unequivocally support the local superiority of IA infusion, a comparative study was started in 1986. Preoperative chemotherapy consisted of 45 mg/m2 of doxorubicin on days 1 and 2; 12 g/m2 of high-dose methotrexate on days 15 and 22; and 3 g/m2 of ifosfamide on days 29, 30, 50, and 51 followed on days 31 and 52 by intravenous (IV) versus IA tourniquet infusion of cisplatin (DDP). A strict randomization of patients was not feasible. A balanced distribution of risk factors was strived for by stratifying and allocating the appropriate patients centrally. The infusion time was prolonged from 1 to 5 hours in the IV group, and the DDP dose was reduced from 150 to 120 mg/m2 in both arms when intolerable ototoxicity became apparent. A multivariate analysis was performed to exclude a bias on the response rates from risk factor distribution and from modifications of DDP infusion time and dosage. The overall fraction of histologic good responders (greater than 90% necrosis) was not found to be different after IA versus IV treatment (34/50 [68%] vs. 41/59 [69%]). Intraarterial instead of IV use of DDP within an aggressive systemic treatment does not seem to improve the local tumor response.

Solubility of H2O and CO2 in ultrapotassic melts at 1200 and 1250 °C and pressure from 50 to 500 MPa

Abstract: The solubility of H2O-CO2 fluids in a synthetic analogue of a phono-tephritic lava composition from Alban Hills (Central Italy) was experimentally determined from 50 to 500 MPa, at 1200 and 1250 °C. Contents of H2O and CO2in experimental glasses were determined by bulk-analytical methods and FTIR spectroscopy. For the quantification of volatile concentrations by IR spectroscopy, we calibrated the absorption coefficients of water-related and carbon-related bands for phono-tephritic compositions. The determined absorption coefficients are 0.62 ± 0.06 L/(mol·cm) for the band at ~4500 cm−1 (OH groups) and 1.02 ± 0.03 L/(mol·cm) for the band at ~5200 cm−1 (H2O molecules). The coefficient for the fundamental OH-stretching vibration at 3550 cm−1 is 63.9 ± 5.4 L/(mol·cm). CO2 is bound in the phono-tephritic glass as CO32− exclusively; its concentration was quantified by the peak height of the doublet near the 1500 cm−1 band with the calibrated absorption coefficient of 308 ± 110 L/(mol·cm). Quench crystals were observed in glasses with water contents exceeding 6 wt% even when using a rapid-quench device, limiting the application of IR spectroscopy for water-rich glasses. H2O solubility in the ultrapotassic melts (7.52 wt% K2O) as a function of pressure is similar to the solubility in basaltic melts up to 400 MPa (~8 wt%) but is higher at 500 MPa (up to 10.71 wt%). At 500 MPa and 1200 °C, the CO2 capacity of the phono-tephritic melt is about 0.82 wt%. The high CO2 capacity is probably related to the high K2O content of the melt. At both 200 and 500 MPa, the H2O solubility shows a non linear dependence on XH2Of in the whole XH2Of range. The variation of CO2 solubility with XCO2f displays a pronounced convex shape especially at 500 MPa, implying that dissolved H2O promotes the solubility of CO2. Our experimental data on CO2 solubility indicate that the interaction between phono-tephritic magma and carbonate rocks occurring in the Alban Hills magmatic system may result in partial dissolution of CO2 from limestone into the magma. However, although the CO2 solubility in phono-tephritic melts is relatively high compared to that in silicic to basaltic melts, the capacity for assimilation of limestone without degassing is nevertheless limited to <1 wt% at the P - T conditions of the magma chamber below Alban Hills.

Search for gravitational waves from low mass binary coalescences in the first year of LIGO's S5 data

Abstract: We have searched for gravitational waves from coalescing low mass compact binary systems with a total mass between 2M_([sun]) and 35Mz-([sun]) and a minimum component mass of 1M_([sun]) using data from the first year of the fifth science run of the three LIGO detectors, operating at design sensitivity. Depending on the mass, we are sensitive to coalescences as far as 150 Mpc from the Earth. No gravitational-wave signals were observed above the expected background. Assuming a population of compact binary objects with a Gaussian mass distribution representing binary neutron star systems, black hole–neutron star binary systems, and binary black hole systems, we calculate the 90% confidence upper limit on the rate of coalescences to be 3.9×10^(-2) yr^(-1)L_(10)^(-1), 1.1×10^(-2) yr^(-1)L_(10)^(-1), and 2.5×10^(-3)yr^(-1)L_(10)^(-1), respectively, where L_(10) is 10^(10) times the blue solar luminosity. We also set improved upper limits on the rate of compact binary coalescences per unit blue-light luminosity, as a function of mass.