@article{ReisgenSchleserAbdurakhmanovetal.2012, author = {Reisgen, Uwe and Schleser, Markus and Abdurakhmanov, Aydemir and Gumenyuk, Andrey}, title = {Measuring of plasma properties induced by non-vacuum electron beam welding}, series = {Physics of plasma}, volume = {19}, journal = {Physics of plasma}, number = {1}, publisher = {AIP Publishing}, address = {Melville, NY}, issn = {1089-7674 (E-Journal); 1070-664X (Print)}, doi = {10.1063/1.3675874}, pages = {1 -- 7}, year = {2012}, abstract = {Electron beam plasma measurement was realised by means of DIABEAM system invented by ISF RWTH Aachen. The Langmuir probe method is used for measurement. The relative simplicity of the method and the possibility of dispersion of high power on the probe allow its application for the investigation of high-power electron beams. The key element of the method is a rotating thin tungsten wire, which intersects the beam transversely on its axis and collects part of the current by itself. The signals, which are registered in the DIABEAM as a voltage, were taken in the form of amplitude. The conversion of the probe current into the distribution along the beam radius was realised using the Abel's method. A voltage-current characteristic was built for the beam current. The local electron density as well as the electron temperature, the floating potential and the plasma potential were measured and calculated by means of this characteristic.}, language = {en} } @article{ReisgenSchleserMokrovetal.2012, author = {Reisgen, Uwe and Schleser, Markus and Mokrov, Oleg and Zabirov, Alexander and F{\"u}ssel, Uwe and Schnick, Michael and Hertel, Martin and Jaeckel, Sebastian}, title = {Modelling and visualisation of the GMA process}, series = {Welding and Cutting}, volume = {11}, journal = {Welding and Cutting}, number = {4}, publisher = {DVS Verlag}, address = {D{\"u}sseldorf}, issn = {1612-3433}, pages = {242 -- 249}, year = {2012}, language = {en} } @article{BorgmeierBongaertsMeinhardt2012, author = {Borgmeier, Claudia and Bongaerts, Johannes and Meinhardt, Friedhelm}, title = {Genetic analysis of the Bacillus licheniformis degSU operon and the impact of regulatory mutations on protease production}, series = {Journal of biotechnology}, volume = {159}, journal = {Journal of biotechnology}, number = {1-2}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-4863 (E-Journal); 0168-1656 (Print)}, doi = {10.1016/j.jbiotec.2012.02.011}, pages = {12 -- 20}, year = {2012}, abstract = {Disruption experiments targeted at the Bacillus licheniformis degSU operon and GFP-reporter analysis provided evidence for promoter activity immediately upstream of degU. pMutin mediated concomitant introduction of the degU32 allele - known to cause hypersecretion in Bacillus subtilis - resulted in a marked increase in protease activity. Application of 5-fluorouracil based counterselection through establishment of a phosphoribosyltransferase deficient Δupp strain eventually facilitated the marker-free introduction of degU32 leading to further protease enhancement achieving levels as for hypersecreting wild strains in which degU was overexpressed. Surprisingly, deletion of rapG - known to interfere with DegU DNA-binding in B. subtilis - did not enhance protease production neither in the wild type nor in the degU32 strain. The combination of degU32 and Δupp counterselection in the type strain is not only equally effective as in hypersecreting wild strains with respect to protease production but furthermore facilitates genetic strain improvement aiming at biological containment and effectiveness of biotechnological processes.}, language = {en} } @article{BoettcherHaselhuhnJakseetal.2012, author = {Boettcher, Martin and Haselhuhn, Angelika and Jakse, Gerhard and Brehmer, Bernhard and Kirschner-Hermanns, Ruth}, title = {Overactive bladder syndrome: an underestimated long-term problem after treatment of patients with localized prostate cancer?}, series = {BJU international}, volume = {109}, journal = {BJU international}, number = {12}, publisher = {Wiley-Blackwell}, address = {Oxford}, issn = {1365-2176 (E-Journal); 1464-410X (E-Journal); 0007-1331 (Print); 1464-4096 (Print)}, doi = {10.1111/j.1464-410X.2011.10623.x}, pages = {1824 -- 1830}, year = {2012}, abstract = {In this study we observed courses of micturition symptoms and differentiated degrees of symptoms for each point in time while also considering the impact of bothersomeness. Our data show that not only significantly more patients who have undergone BT suffer from OAB than those who have undergone RP, but also that those affected show significantly higher values for severity of OAB symptoms throughout the whole observation period of 36 months. Our data analysis further shows that variability of OAB symptoms as well as fluctuation of severity of OAB symptoms vary to a significantly higher degree after BT than after RP. Looking only at mean figures at a given point in time clearly underestimates the underlying problem. This fact is not reflected in the literature.}, language = {en} } @article{OertelBung2012, author = {Oertel, Mario and Bung, Daniel B.}, title = {Initial stage of two-dimensional dam-break waves: laboratory versus VOF}, series = {Journal of hydraulic research}, volume = {50}, journal = {Journal of hydraulic research}, number = {1}, publisher = {Taylor \& Francis}, address = {London}, issn = {1814-2079 (E-Journal); 0022-1686 (Print)}, doi = {10.1080/00221686.2011.639981}, pages = {89 -- 97}, year = {2012}, abstract = {Since several decades, dam-break waves have been of main research interest. Mathematical approaches have been developed by analytical, physical and numerical models within the past 120 years. During the past 10 years, the number of research investigations has increased due to improved measurement techniques as well as significantly increased computer memories and performances. In this context, the present research deals with the initial stage of two-dimensional dam-break waves by comparing physical and numerical model results as well as analytical approaches. High-speed images and resulting particle image velocimetry calculations are thereby compared with the numerical volume-of-fluid (VOF) method, included in the commercial code FLOW-3D. Wave profiles and drag forces on placed obstacles are analysed in detail. Generally, a good agreement between the laboratory and VOF results is found.}, language = {en} } @article{HoetterFateriGebhardt2012, author = {H{\"o}tter, Jan-Steffen and Fateri, Miranda and Gebhardt, Andreas}, title = {Selective laser melting of metals: desktop machines open up new chances even for small companies}, series = {Advanced materials research}, volume = {622-623}, journal = {Advanced materials research}, publisher = {Trans Tech Publ.}, address = {Baech}, issn = {1662-8985 (E-Journal); 1022-6680 (Print)}, doi = {10.4028/www.scientific.net/AMR.622-623.461}, pages = {461 -- 465}, year = {2012}, abstract = {Additive manufacturing (AM) of metal parts by using Selective Laser Melting (SLM) has become a powerful tool mostly in the area of automotive, aerospace engineering and others. Especially in the field of dentistry, jewelry and related branches that require individualized or even one-of-a-kind products, the direct digital manufacturing process opens up new ways of design and manufacturing. In these fields, mostly small and medium sized businesses (SME) are operating which do not have sufficient human and economic resources to invest in this technology. But to stay competitive, the application of AM can be regarded as a necessity. In this situation a new desktop machine (Realizer SLM 50) was introduced that cost about 1/3 of a shop floor SLM machine and promises small quality parts. To find out whether the machine really is an alternative for SMEs the University of Applied Science, Aachen, Germany, designed, build and optimized typical parts from the dentistry and the jewelry branches using CoCr and silver material, the latter being new with this application. The paper describes the SLM procedure and how to find and optimize the most important parameters. The test is accompanied by digital simulation in order to verify the build parameters and to plan future builds. The procedure is shown as well as the resulting parts made from CoCr and silver material.}, language = {en} } @article{RibitschHeumannKarletal.2012, author = {Ribitsch, D. and Heumann, S. and Karl, W. and Gerlach, J. and Leber, R. and Birner-Gruenberger, R. and Gruber, K. and Eiteljoerg, I. and Remler, P. and Siegert, Petra and Lange, J. and Maurer, Karl-Heinz and Berg, G. and Guebitz, G. M. and Schwab, H.}, title = {Extracellular serine proteases from Stenotrophomonas maltophilia: Screening, isolation and heterologous expression in E. coli}, series = {Journal of biotechnology}, volume = {157}, journal = {Journal of biotechnology}, number = {1}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-4863 (E-Journal); 0168-1656 (Print)}, doi = {10.1016/j.jbiotec.2011.09.025}, pages = {140 -- 147}, year = {2012}, abstract = {A large strain collection comprising antagonistic bacteria was screened for novel detergent proteases. Several strains displayed protease activity on agar plates containing skim milk but were inactive in liquid media. Encapsulation of cells in alginate beads induced protease production. Stenotrophomonas maltophilia emerged as best performer under washing conditions. For identification of wash-active proteases, four extracellular serine proteases called StmPr1, StmPr2, StmPr3 and StmPr4 were cloned. StmPr2 and StmPr4 were sufficiently overexpressed in E. coli. Expression of StmPr1 and StmPr3 resulted in unprocessed, insoluble protein. Truncation of most of the C-terminal domain which has been identified by enzyme modeling succeeded in expression of soluble, active StmPr1 but failed in case of StmPr3. From laundry application tests StmPr2 turned out to be a highly wash-active protease at 45 °C. Specific activity of StmPr2 determined with suc-l-Ala-l-Ala-l-Pro-l-Phe-p-nitroanilide as the substrate was 17 ± 2 U/mg. In addition we determined the kinetic parameters and cleavage preferences of protease StmPr2.}, language = {en} } @article{SchmitzWeber2012, author = {Schmitz, Philipp and Weber, Martin}, title = {Buying and selling behavior of individual investors in option-like securities}, series = {Die Betriebswirtschaft : DBW}, volume = {72}, journal = {Die Betriebswirtschaft : DBW}, number = {5}, publisher = {Sch{\"a}ffer-Poeschel}, address = {Stuttgart}, issn = {0342-7064}, doi = {10.2139/ssrn.2055088}, pages = {409 -- 426}, year = {2012}, abstract = {We analyze the trading behavior of individual investors in option-like securities, namely bankissued warrants, and thus expand the growing literature of investors behavior to a new kind of securities. A unique data set from a large German discount broker gives us the opportunity to analyze the trading behavior of 1,454 investors, making 89,958 transactions in 6,724 warrants on 397 underlyings. In different logit regression, we make use of the facts that investors can speculate on rising and falling prices of the underlying with call and put warrants and that we also have information about the stock portfolios of the investors. We report several facts about the trading behavior of individual investors in warrants that are consistent with the literature on the behavior of individual investors in the stock market. The warrant investors buy calls and sell puts if the price of the underlying has decreased over the past trading days and they sell calls and buy puts if the price of the underlying has increased. That means, the investors follow negative feedback trading strategies in all four trading categories observed. In addition, we find strong evidence for the disposition effect for call as well as put warrants, which is reversed in December. The trading behavior is also influenced if the underlying reaches some exceptionally prices, e.g. highs, lows or the strike price. We show that hedging, as one natural candidate to buy puts, does not play an important role in the market for bank-issued warrants.}, language = {en} } @article{EilmannRigling2012, author = {Eilmann, Britta and Rigling, Andreas}, title = {Tree-growth analyses to estimate tree species' drought tolerance}, series = {Tree Physiology}, volume = {32}, journal = {Tree Physiology}, number = {2}, editor = {Abrams, Marc}, publisher = {Oxford University Press}, address = {Oxford}, issn = {0829-318X (Print)}, doi = {10.1093/treephys/tps004}, pages = {178 -- 187}, year = {2012}, abstract = {Climate change is challenging forestry management and practices. Among other things, tree species with the ability to cope with more extreme climate conditions have to be identified. However, while environmental factors may severely limit tree growth or even cause tree death, assessing a tree species' potential for surviving future aggravated environmental conditions is rather demanding. The aim of this study was to find a tree-ring-based method suitable for identifying very drought-tolerant species, particularly potential substitute species for Scots pine (Pinus sylvestris L.) in Valais. In this inner-Alpine valley, Scots pine used to be the dominating species for dry forests, but today it suffers from high drought-induced mortality. We investigate the growth response of two native tree species, Scots pine and European larch (Larix decidua Mill.), and two non-native species, black pine (Pinus nigra Arnold) and Douglas fir (Pseudotsuga menziesii Mirb. var. menziesii), to drought. This involved analysing how the radial increment of these species responded to increasing water shortage (abandonment of irrigation) and to increasingly frequent drought years. Black pine and Douglas fir are able to cope with drought better than Scots pine and larch, as they show relatively high radial growth even after irrigation has been stopped and a plastic growth response to drought years. European larch does not seem to be able to cope with these dry conditions as it lacks the ability to recover from drought years. The analysis of trees' short-term response to extreme climate events seems to be the most promising and suitable method for detecting how tolerant a tree species is towards drought. However, combining all the methods used in this study provides a complete picture of how water shortage could limit species.}, language = {en} } @article{BragardvanHoekDeDoncker2012, author = {Bragard, Michael and van Hoek, H. and De Doncker, R. W.}, title = {A major design step in IETO concept realization that allows overcurrent protection and pushes limits of switching performance}, series = {IEEE transactions on power electronics}, volume = {27}, journal = {IEEE transactions on power electronics}, number = {9}, publisher = {IEEE}, address = {New York}, issn = {0885-8993}, doi = {10.1109/TPEL.2012.2189136}, pages = {4163 -- 4171}, year = {2012}, abstract = {This paper presents the latest prototype of the integrated emitter turn-off thyristor concept, which potentially ranks among thyristor high-power devices like the gate turn-off thyristor and the integrated gate-commutated thyristor (IGCT). Due to modifications of the external driver stage and mechanical press-pack design optimization, this prototype allows for full device characterization. The turn-off capability was increased to 1600 A with an active silicon area of 823mm2 . This leads to a transient peak power of 672.1kW/cm² . Within this paper, measurements and concept assessment are presented and a comparison to state-of-the-art IGCT devices is provided.}, language = {en} } @article{RiglingBiglerEilmannetal.2012, author = {Rigling, Andreas and Bigler, Christof and Eilmann, Britta and Feldmeyer-Christe, Elisabeth and Gimmi, Urs and Ginzler, Christian and Graf, Ulrich and Mayer, Phillip and Vacchiano, Giorgio and Weber, Pascal and Wohlgemuth, Thomas and zweifel, Roman and Dobbertin, Matthias}, title = {Driving factors of a vegetation shift from Scots pine to pubescent oak in dry Alpine forests}, series = {Global Change Biology}, volume = {19}, journal = {Global Change Biology}, number = {1}, publisher = {Wiley-Blackwell}, address = {Oxford}, issn = {1354-1013 (Print)}, doi = {10.1111/gcb.12038}, pages = {229 -- 240}, year = {2012}, abstract = {An increasing number of studies have reported on forest declines and vegetation shifts triggered by drought. In the Swiss Rhone valley (Valais), one of the driest inner-Alpine regions, the species composition in low elevation forests is changing: The sub-boreal Scots pine (Pinus sylvestris L.) dominating the dry forests is showing high mortality rates. Concurrently the sub-Mediterranean pubescent oak (Quercus pubescens Willd.) has locally increased in abundance. However, it remains unclear whether this local change in species composition is part of a larger-scale vegetation shift. To study variability in mortality and regeneration in these dry forests we analysed data from the Swiss national forest inventory (NFI) on a regular grid between 1983 and 2003, and combined it with annual mortality data from a monitoring site. Pine mortality was found to be highest at low elevation (below 1000 m a.s.l.). Annual variation in pine mortality was correlated with a drought index computed for the summer months prior to observed tree death. A generalized linear mixed-effects model indicated for the NFI data increased pine mortality on dryer sites with high stand competition, particularly for small-diameter trees. Pine regeneration was low in comparison to its occurrence in the overstorey, whereas oak regeneration was comparably abundant. Although both species regenerated well at dry sites, pine regeneration was favoured at cooler sites at higher altitude and oak regeneration was more frequent at warmer sites, indicating a higher adaptation potential of oaks under future warming. Our results thus suggest that an extended shift in species composition is actually occurring in the pine forests in the Valais. The main driving factors are found to be climatic variability, particularly drought, and variability in stand structure and topography. Thus, pine forests at low elevations are developing into oak forests with unknown consequences for these ecosystems and their goods and services.}, language = {en} } @article{LeidingerNoistenWollert2012, author = {Leidinger, Rafael and Noisten, Thomas and Wollert, J{\"o}rg}, title = {Realtime automation networks in moVing industrial environments}, series = {Journal of systemics, cybernetics and informatics}, volume = {Vol. 10}, journal = {Journal of systemics, cybernetics and informatics}, number = {Iss. 2}, publisher = {IIIC}, address = {Orlando}, issn = {1690-4532}, pages = {52 -- 56}, year = {2012}, abstract = {The radio-based wireless data communication has made the realization of new technical solutions possible in many fields of the automation technology (AT). For about ten years, a constant disproportionate growth of wireless technologies can be observed in the automation technology. However, it shows that especially for the AT, conventional technologies of office automation are unsuitable and/or not manageable. The employment of mobile services in the industrial automation technology has the potential of significant cost and time savings. This leads to an increased productivity in various fields of the AT, for example in the factory and process automation or in production logistics. In this paper technologies and solutions for an automation-suited supply of mobile wireless services will be introduced under the criteria of real time suitability, IT-security and service orientation. Emphasis will be put on the investigation and development of wireless convergence layers for different radio technologies, on the central provision of support services for an easy-to-use, central, backup enabled management of combined wired / wireless networks and on the study on integrability in a Profinet real-time Ethernet network.}, language = {en} } @article{MottaghyDijkshoorn2012, author = {Mottaghy, Darius and Dijkshoorn, Lydia}, title = {Implementing an effective finite difference formulation for borehole heat exchangers into a heat and mass transport code}, series = {Renewable Energy}, volume = {45}, journal = {Renewable Energy}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0960-1481}, doi = {10.1016/j.renene.2012.02.013}, pages = {59 -- 71}, year = {2012}, abstract = {We present an effective finite difference formulation for implementing and modeling multiple borehole heat exchangers (BHE) in the general 3-D coupled heat and flow transport code SHEMAT. The BHE with arbitrary length can be either coaxial or double U-shaped. It is particularly suitable for modeling deep BHEs which contain varying pipe diameters and materials. Usually, in numerical simulations, a fine discretization of the BHE assemblage is required, due to the large geometric aspect ratios involved. This yields large models and long simulation times. The approach avoids this problem by considering heat transport between fluid and the soil through pipes and grout via thermal resistances. Therefore, the simulation time can be significantly reduced. The coupling with SHEMAT is realized by introducing an effective heat generation. Due to this connection, it is possible to consider heterogeneous geological models, as well as the influence of groundwater flow. This is particularly interesting when studying the long term behavior of a single BHE or a BHE field. Heating and cooling loads can enter the model with an arbitrary interval, e.g. from hourly to monthly values. When dealing with large BHE fields, computing times can be further significantly reduced by focusing on the temperature field around the BHEs, without explicitly modeling inlet and outlet temperatures. This allows to determine the possible migration of cold and warm plumes due to groundwater flow, which is of particular importance in urban areas with a high BHE installation density. The model is validated against the existing BHE modeling codes EWS and EED. A comparison with monitoring data from a deep BHE in Switzerland shows a good agreement. Synthetic examples demonstrate the field of application of this model.}, language = {en} } @article{HenkenOosterhuisOehlschlaegeretal.2012, author = {Henken, F. E. and Oosterhuis, K. and {\"O}hlschl{\"a}ger, Peter and Bosch, L. and Hooijberg, E. and Haanen, J. B. A. G. and Steenbergen, R. D. M.}, title = {Preclinical safety evaluation of DNA vaccines encoding modified HPV16 E6 and E7}, series = {Vaccine}, volume = {30}, journal = {Vaccine}, number = {28}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0264-410X}, doi = {10.1016/j.vaccine.2012.04.013}, pages = {4259 -- 4266}, year = {2012}, abstract = {Persistent infection with high-risk human papillomaviruses (hrHPV) can result in the formation of anogenital cancers. As hrHPV proteins E6 and E7 are required for cancer initiation and maintenance, they are ideal targets for immunotherapeutic interventions. Previously, we have described the development of DNA vaccines for the induction of HPV16 E6 and E7 specific T cell immunity. These vaccines consist of 'gene-shuffled' (SH) versions of HPV16 E6 and E7 that were fused to Tetanus Toxin Fragment C domain 1 (TTFC) and were named TTFC-E6SH and TTFC-E7SH. Gene-shuffling was performed to avoid the risk of inducing malignant transformation at the vaccination site. Here, we describe the preclinical safety evaluation of these candidate vaccines by analysis of their transforming capacity in vitro using established murine fibroblasts (NIH 3T3 cells) and primary human foreskin keratinocytes (HFKs). We demonstrate that neither ectopic expression of TTFC-E6SH and TTFC-E7SH alone or in combination enabled NIH 3T3 cells to form colonies in soft agar. In contrast, expression of HPV16 E6WT and E7WT alone or in combination resulted in effective transformation. Similarly, retroviral transduction of HFKs from three independent donors with both TTFC-E6SH and TTFC-E7SH alone or in combination did not show any signs of immortalization. In contrast, the combined expression of E6WT and E7WT induced immortalization in HFKs from all donors. Based on these results we consider it justified to proceed to clinical evaluation of DNA vaccines encoding TTFC-E6SH and TTFC-E7SH in patients with HPV16 associated (pre)malignancies.}, language = {en} } @article{ImmelGruetzkeSpaeteetal.2012, author = {Immel, Timo and Gr{\"u}tzke, Martin and Sp{\"a}te, Anne-Katrin and Groth, Ulrich and {\"O}hlschl{\"a}ger, Peter and Huhn, Thomas}, title = {Synthesis and X-ray structure analysis of a heptacoordinate titanium(IV)-bis-chelate with enhanced in vivo antitumor efficacy}, series = {Chemical Communications}, volume = {48}, journal = {Chemical Communications}, number = {46}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1364-548X}, doi = {10.1039/C2CC31624B}, pages = {5790 -- 5792}, year = {2012}, abstract = {Chelate stabilization of a titanium(IV)-salan alkoxide by ligand exchange with 2,6-pyridinedicarboxylic acid (dipic) resulted in heptacoordinate complex 3 which is not redox-active, stable on silica gel and has increased aqueous stability. 3 is highly toxic in HeLa S3 and Hep G2 and has enhanced antitumor efficacy in a mouse cervical-cancer model.}, language = {en} } @article{Staat2012, author = {Staat, Manfred}, title = {Limit and shakedown analysis under uncertainty}, series = {Tap chi Khoa hoc \& ung dung - Dai hoc Ton Duc Thang}, volume = {19}, journal = {Tap chi Khoa hoc \& ung dung - Dai hoc Ton Duc Thang}, pages = {45 -- 47}, year = {2012}, language = {en} } @article{OrzadaMaderwaldPoseretal.2012, author = {Orzada, S. and Maderwald, S. and Poser, B. A. and Johst, S. and Kannengiesser, S. and Ladd, M. E. and Bitz, Andreas}, title = {Time-interleaved acquisition of modes: an analysis of SAR and image contrast implications}, series = {Magnetic Resonance in Medicine}, volume = {67}, journal = {Magnetic Resonance in Medicine}, number = {4}, publisher = {Wiley-Liss}, address = {New York}, issn = {1522-2594}, doi = {10.1002/mrm.23081}, pages = {1033 -- 1041}, year = {2012}, abstract = {s the magnetic field strength and therefore the operational frequency in MRI are increased, the radiofrequency wavelength approaches the size of the human head/body, resulting in wave effects which cause signal decreases and dropouts. Especially, whole-body imaging at 7 T and higher is therefore challenging. Recently, an acquisition scheme called time-interleaved acquisition of modes has been proposed to tackle the inhomogeneity problems in high-field MRI. The basic premise is to excite two (or more) different Burn:x-wiley:07403194:media:MRM23081:tex2gif-stack-1 modes using static radiofrequency shimming in an interleaved acquisition, where the complementary radiofrequency patterns of the two modes can be exploited to improve overall signal homogeneity. In this work, the impact of time-interleaved acquisition of mode on image contrast as well as on time-averaged specific absorption rate is addressed in detail. Time-interleaved acquisition of mode is superior in Burn:x-wiley:07403194:media:MRM23081:tex2gif-stack-2 homogeneity compared with conventional radiofrequency shimming while being highly specific absorption rate efficient. Time-interleaved acquisition of modes can enable almost homogeneous high-field imaging throughout the entire field of view in PD, T2, and T2*-weighted imaging and, if a specified homogeneity criterion is met, in T1-weighted imaging as well.}, language = {en} } @article{KobusBitzUdenetal.2012, author = {Kobus, Thiele and Bitz, Andreas and Uden, Mark J. van and Lagemaat, Miram W. and Rothgang, Eva and Orzada, Stephan and Heerschap, Arend and Scheenen, Tom W. J.}, title = {In vivo 31P MR spectroscopic imaging of the human prostate at 7 T: safety and feasibility}, series = {Magnetic Resonance in Medicine}, volume = {68}, journal = {Magnetic Resonance in Medicine}, number = {6}, publisher = {Wiley-Liss}, address = {New York}, issn = {1522-2594}, doi = {10.1002/mrm.24175}, pages = {1683 -- 1695}, year = {2012}, abstract = {31P MR spectroscopic imaging of the human prostate provides information about phosphorylated metabolites that could be used for prostate cancer characterization. The sensitivity of a magnetic field strength of 7 T might enable 3D 31P MR spectroscopic imaging with relevant spatial resolution in a clinically acceptable measurement time. To this end, a 31P endorectal coil was developed and combined with an eight-channel 1H body-array coil to relate metabolic information to anatomical location. An extensive safety validation was performed to evaluate the specific absorption rate, the radiofrequency field distribution, and the temperature distribution of both coils. This validation consisted of detailed Finite Integration Technique simulations, confirmed by MR thermometry and Burn:x-wiley:07403194:media:MRM24175:tex2gif-stack-1 measurements in a phantom and in vivo temperature measurements. The safety studies demonstrated that the presence of the 31P endorectal coil had no influence on the specific absorption rate levels and temperature distribution of the external eight-channel 1H array coil. To stay within a 10 g averaged local specific absorption rate of 10 W/kg, a maximum time-averaged input power of 33 W for the 1H array coil was allowed. For transmitting with the 31P endorectal coil, our safety limit of less than 1°C temperature increase in vivo during a 15-min MR spectroscopic imaging experiment was reached at a time-averaged input power of 1.9 W. With this power setting, a second in vivo measurement was performed on a healthy volunteer. Using adiabatic excitation, 3D 31P MR spectroscopic imaging produced spectra from the entire prostate in 18 min with a spatial resolution of 4 cm3. The spectral resolution enabled the separate detection of phosphocholine, phosphoethanolamine, inorganic phosphate, and other metabolites that could play an important role in the characterization of prostate cancer.}, language = {en} } @article{YazdanbakhshSolbachBitz2012, author = {Yazdanbakhsh, Pedram and Solbach, Klaus and Bitz, Andreas}, title = {Variable power combiner for RF mode shimming in 7-T MR imaging}, series = {IEEE Transaction on Biomedical Engineering}, volume = {59}, journal = {IEEE Transaction on Biomedical Engineering}, number = {9}, publisher = {IEEE}, address = {New York}, issn = {1558-2531}, doi = {10.1109/TBME.2012.2205926}, pages = {2549 -- 2557}, year = {2012}, abstract = {This contribution discusses the utilization of RF power in an MRI system with RF mode shimming which enables the superposition of circularly polarized modes of a transmit RF coil array driven by a Butler matrix. Since the required power for the individual modes can vary widely, mode-shimming can result in a significant underutilization of the total available RF power. A variable power combiner (VPC) is proposed to improve the power utilization: it can be realized as a reconfiguration of the MRI transmit system by the inclusion of one additional matrix network which receives the power from all transmit amplifiers at its input ports and provides any desired (combined) power distribution at its output ports by controlling the phase and amplitude of the amplifiers' input signals. The power distribution at the output ports of the VPC is then fed into the "mode" ports of the coil array Butler matrix in order to superimpose the spatial modes at the highest achievable power utilization. The VPC configuration is compared to the standard configuration of the transmit chain of our MRI system with 8 transmit channels and 16 coils. In realistic scenarios, improved power utilization was achieved from 17\% to 60\% and from 14\% to 55\% for an elliptical phantom and a region of interest in the abdomen, respectively, and an increase of the power utilization of 1 dB for a region of interest in the upper leg. In general, it is found that the VPC allows significant improvement in power utilization when the shimming solution demands only a few modes to be energized, while the technique can yield loss in power utilization in cases with many modes required at high power level.}, language = {en} } @article{PaulssenKongArciszewskietal.2012, author = {Paulßen, Elisabeth and Kong, Shushu and Arciszewski, Pawel and Wielbalck, Swantje and Abram, Ulrich}, title = {Aryl and NHC Compounds of Technetium and Rhenium}, series = {Journal of the American Chemical Society}, volume = {134}, journal = {Journal of the American Chemical Society}, number = {22}, publisher = {ACS Publications}, address = {Washington, DC}, issn = {1520-5126}, doi = {10.1021/ja3033718}, pages = {9118 -- 9121}, year = {2012}, abstract = {Air- and water-stable phenyl complexes with nitridotechnetium(V) cores can be prepared by straightforward procedures. [TcNPh2(PPh3)2] is formed by the reaction of [TcNCl2(PPh3)2] with PhLi. The analogous N-heterocyclic carbene (NHC) compound [TcNPh2(HLPh)2], where HLPh is 1,3,4-triphenyl-1,2,4-triazol-5-ylidene, is available from (NBu4)[TcNCl4] and HLPh or its methoxo-protected form. The latter compound allows the comparison of different Tc-C bonds within one compound. Surprisingly, the Tc chemistry with such NHCs does not resemble that of corresponding Re complexes, where CH activation and orthometalation dominate.}, language = {en} }