Cyclische Diazastannylene. - XI : Ringe und Käfige mit Dimethylbis(methylamido)silan-Liganden am zweiwertigen Zinn

SnCl2 und (LiNMe)2SiMe2 (Me = CH3) reagieren unter Abspaltung von LiCl zu dem molekularen Polycyclus (Me2Si)3(NMe)5Sn2 (I) und zu polymerem (SnNMe)n (II). I kann auch durch Einwirkung von Dimethylbis(methylamino)-silan auf das stannylen Me2Si(NCMe3)2Sn dargestellt werden, wobei weiterhin der Käfig (Me2Si)(NMe)5Sn4 (III) entsteht, wenn ohne Lösungsmittel gearbeitet wird. Auf Grund von 1H-NMR-Spectren und einer Röntgenstrukturanalyse ergeben sich für I und III folgende Strukturen: das Molekülgerüst von I besteht aus einem Sn2N2-Vierring, der in 1,3-Position die Atomsequenz ---Si---N---Si--- und in 2,4-Position ---N—Si---N--- als Brücken trägt; III hat die Structur eines "Basketans\u27;: vier tetraedrisch ausgerichtete Zinnatome und vier Stickstoffatome bilden einen Würfel, in dessen eine Kante eine MeNSiMe2-Einheit eingeschoben ist. Die NMR-Spectren zeigen an, dass in III bei Zimmertemperatur in organischen Lösungsmitteln Bindungsfluktuationen auftreten

Aufbau und Management von Innovationskompetenz bei radikalen Innovationsprojekten

Auf dynamischen Märkten müssen Unternehmen ihre etablierten Wettbewerbsvorteile ständig erneuern. Dabei sind Innovationen ein wesentlicher Erfolgsfaktor für Wachstum und Fortschritt. Die Realisierung von inkrementellen Innovationen, die das bestehende Geschäft weiterentwickeln, als auch von radikalen Innovationen, die neue Geschäftsfelder erschließen, ist dabei die Voraussetzung für den langfristigen Erfolg. Das Management von radikalen Innovationsprojekten stellt eine große Herausforderung dar. Hohe Unsicherheiten auf den Feldern Technologie und Markt paaren sich mit geringen Erfahrungen in dem neuen Tätigkeitsfeld. Gerade zu Beginn eines radikalen Innovationsprojektes bestehen im Unternehmen umfassende Kompetenzlücken. In dieser Dissertation wird ein kompetenzorientierter Ansatz entwickelt, der die spezifischen Anforderungen von radikalen Innovationsprojekten berücksichtigt. Die Arbeit beginnt dabei mit der Betrachtung relevanter Literatur im Bereich der Kompetenz- und Innovationsforschung. Nachfolgend wird ein Modell der Innovationskompetenz entwickelt. Auf dem Modell aufbauend werden sieben radikale Innovationsprojekte in Form einer wissenschaftlichen Forschungsfallstudie untersucht. Die Ergebnisse werden dazu genutzt, Hypothesen für die Forschung und Gestaltungshinweise für das Management zu entwickeln. Die Arbeit bietet mit der Entwicklung des Modells der Innovationskompetenz und dem Entwickeln von Hypothesen einen wesentlichen Beitrag für die Innovationsforschung. Weiterhin werden wertvolle Hinweise für die Realisierung von radikalen Innovationsprojekten in der Unternehmenspraxis gegeben

Systematic evaluation of 99mTc-tetrofosmin versus 99mTc-sestamibi to study murine myocardial perfusion in small animal SPECT/CT

Background: The “back-translation” of clinically available protocols to measure myocardial perfusion to preclinical imaging in mouse models of human disease is attractive for basic biomedical research. With respect to singlephoton emission computed tomography (SPECT) approaches, clinical myocardial perfusion imaging protocols are established with different 99mTc-labeled perfusion tracers; however, studies evaluating and optimizing protocols for these tracers in high-resolution pinhole SPECT in mice are lacking. This study aims at evaluating two clinically available 99mTc-labeled myocardial perfusion tracers (99mTc-sestamibi vs. 99mTc-Tetrofosmin) in mice using four different imaging protocols. Methods: Adult C57BL/6 male mice were injected with 99mTc-sestamibi (MIBI) or 99mTc-Tetrofosmin (TETRO) (4 MBq/g body weight) either intravenously through the tail vein (n = 5) or retroorbitally (n = 5) or intraperitoneally (i. p.) under anesthesia (n = 3) or i.p. in an awake state (n = 3) at rest. Immediately after injection, a multi-frame singlephoton emission computed tomography/computed tomography (SPECT/CT) acquisition was initiated with six subsequent time frames of 10 min each. Reconstructed images of the different protocols were assessed and compared by visual analysis by experts and by time-activity-curves generated from regions-of-interest for various organs (normalized uptake values). Results: Visually assessing overall image quality, the best image quality was found for MIBI for both intravenous injection protocols, whereas TETRO only had comparable image quality after retroorbital injections. These results were confirmed by quantitative analysis where left ventricular (LV) uptake of MIBI after tail vein injections was found significantly higher for all time points accompanied with a significantly slower washout of 16% for MIBI vs. 33% for TETRO (p = 0.009) from 10 to 60 min post injection (PI). Interestingly, LV washout from 10 to 60 min PI was significantly higher for TETRO when applied by tail vein injections when compared to retroorbital injections (22%, p = 0.008). However, liver uptake was significant and comparable for both tracers at all time points. Radioactivity concentration in the lungs was negligible for all time points and both tracers. Conclusion: Intravenous MIBI injection (both tail vein and retroorbital) results in the best image quality for assessing myocardial perfusion of the murine heart by SPECT/CT. TETRO has a comparable image quality only for the retroorbital injection route

NOX2-derived reactive oxygen species are crucial for CD29-induced pro-survival signalling in cardiomyocytes

Aims The highly expressed cell adhesion receptor CD29 (β1-integrin) is essential for cardiomyocyte growth and survival, and its loss of function causes severe heart disease. However, CD29-induced signalling in cardiomyocytes is ill defined and may involve reactive oxygen species (ROS). A decisive source of cardiac ROS is the abundant NADPH oxidase (NOX) isoform NOX2. Because understanding of NOX-derived ROS in the heart is still poor, we sought to test the role of ROS and NOX in CD29-induced survival signalling in cardiomyocytes. Methods and results In neonatal rat ventricular myocytes, CD29 activation induced intracellular ROS formation (oxidative burst) as assessed by flow cytometry using the redox-sensitive fluorescent dye dichlorodihydrofluorescein diacetate. This burst was inhibited by apocynin and diphenylene iodonium. Further, activation of CD29 enhanced NOX activity (lucigenin-enhanced chemiluminescence) and activated the MEK/ERK and PI3K/Akt survival pathways. CD29 also induced phosphorylation of the inhibitory Ser9 on the pro-apoptotic kinase glycogen synthase kinase-3β in a PI3K/Akt- and MEK-dependent manner, and improved cardiomyocyte viability under conditions of oxidative stress. The ROS scavenger MnTMPyP or adenoviral co-overexpression of the antioxidant enzymes superoxide dismutase and catalase inhibited CD29-induced pro-survival signalling. Further, CD29-induced protective pathways were lost in mouse cardiomyocytes deficient for NOX2 or functional p47phox, a regulatory subunit of NOX. Conclusion p47phox-dependent, NOX2-derived ROS are mandatory for CD29-induced pro-survival signalling in cardiomyocytes. These findings go in line with a growing body of evidence suggesting that ROS can be beneficial to the cell and support a crucial role for NOX2-derived ROS in cell survival in the hear

Intraoperative 3-D mapping of parathyroid adenoma using freehand SPECT

Background: Freehand single photon emission computed tomography (fSPECT) is a three-dimensional (3-D) tomographic imaging modality based on data acquisition with a handheld detector that is moved freely, in contrast to conventional, gantry-mounted gamma camera systems. In this pilot study, we evaluated the feasibility of fSPECT for intraoperative 3-D mapping in patients with parathyroid adenomas. Methods: Three patients (range 30 to 45 years) diagnosed with hyperparathyroidism (one primary and two tertiary) underwent parathyroid scintigraphy with technetium-99m sestamibi (99mTc-MIBI) to localize parathyroid adenomas. Two patients were referred with persistent hyperparathyroidism after conventional parathyroidectomy. In all three patients, a planar scintigraphy of the neck was performed 10 min after injection (p.i.) followed by SPECT/CT (Symbia T2, Siemens Healthcare) and a correlative ultrasound 2 h p.i. 99mTc-MIBI scan was performed the day before surgery in two patients and at the same day in one patient. fSPECT images were acquired intraoperatively using declipse SPECT (SurgicEyeTM). Results: A total of five parathyroid adenomas were successfully located with SPECT/CT. fSPECT allowed intraoperative detection of all adenomas, and successful parathyroidectomy was accomplished. Parathyroid hormone level decreased intraoperatively in all three patients, on average, by 79% (range 72% to 91%). Conclusion: In this preliminary study, we could demonstrate that intraoperative localization of parathyroid adenomas is feasible using the freehand SPECT technology, thus allowing an image-guided parathyroidectomy

A Spectroscopic Study of Mass Outflows in the Interacting Binary RY Scuti

The massive interacting binary RY Scuti is an important representative of an active mass-transferring system that is changing before our eyes and which may be an example of the formation of a Wolf-Rayet star through tidal stripping. Utilizing new and previously published spectra, we present examples of how a number of illustrative absorption and emission features vary during the binary orbit. We identify spectral features associated with each component, calculate a new, double-lined spectroscopic binary orbit, and find masses of 7.1 +/- 1.2 M_sun for the bright supergiant and 30.0 +/- 2.1 M_sun for the hidden massive companion. Through tomographic reconstruction of the component spectra from the composite spectra, we confirm the O9.7 Ibpe spectral class of the bright supergiant and discover a B0.5 I spectrum associated with the hidden massive companion; however, we suggest that the latter is actually the spectrum of the photosphere of the accretion torus immediately surrounding the massive companion. We describe the complex nature of the mass loss flows from the system in the context of recent hydrodynamical models for beta Lyr, leading us to conclude RY Scuti has matter leaving the system in two ways: 1) a bipolar outflow from winds generated by the hidden massive companion, and 2) mass from the bright O9.7 Ibpe supergiant flowing from the region near the L2 point to fill out a large, dense circumbinary disk. This circumbinary disk (radius ~ 1 AU) may feed the surrounding double-toroidal nebula (radius ~ 2000 AU).Comment: 41 pages with 7 tables and 11 figures, accepted to Ap

Discretization of variational regularization in Banach spaces

Consider a nonlinear ill-posed operator equation $F(u)=y$ where $F$ is defined on a Banach space $X$. In general, for solving this equation numerically, a finite dimensional approximation of $X$ and an approximation of $F$ are required. Moreover, in general the given data \yd of $y$ are noisy. In this paper we analyze finite dimensional variational regularization, which takes into account operator approximations and noisy data: We show (semi-)convergence of the regularized solution of the finite dimensional problems and establish convergence rates in terms of Bregman distances under appropriate sourcewise representation of a solution of the equation. The more involved case of regularization in nonseparable Banach spaces is discussed in detail. In particular we consider the space of finite total variation functions, the space of functions of finite bounded deformation, and the $L^\infty$--space

Five-Year Outcomes of the SuperB Trial:A Multicenter Randomized Controlled Trial Comparing Heparin-Bonded Endograft to Surgical Femoropopliteal Bypass

Objective: This study aims to compare the 5-year outcomes of endoluminal bypass (EB) using heparin-bonded self-expanding covered stents versus bypass surgery for extensive femoropopliteal disease, including technical and clinical outcomes and health status. Background: The surgical femoropopliteal bypass was the gold standard to treat peripheral arterial disease (PAD) for decades; however, endovascular treatment modalities are now recommended for most femoropopliteal lesions. One-year data of a randomized controlled trial comparing EB with surgical bypass (SB) have shown a faster recovery, less morbidity, and comparable patency rates between the two techniques. To date, long-term randomized controlled data regarding both techniques are lacking. Methods: Five-year results of a multicenter randomized controlled trial comparing EB with SB in patients with femoropopliteal artery disease were evaluated based on intention-to-treat and per-protocol analyses. Results: At 5-year follow-up, primary, primary-assisted, and secondary patency rates were 36.2%, 52.4%, and 68.1% for EB and 49.4%, 72.2%, and 77.8% for SB, respectively (p=0.608). Freedom from target lesion revascularization (fTLR) was 34.1% for EB and 57.6% for SB (p=0.365). In both groups, the ankle-brachial index, Rutherford classification, and walking distance significantly improved compared with baseline without differences between groups at follow-up. Freedom from major amputation rate was 92.6% in the EB group and 96.2% in the SB group (p=0.361). The 36-Item Short-Form Health Survey showed no significant differences between groups. Conclusion: Treatment of extensive femoropopliteal disease with self-expanding covered stents provides comparable clinical-related and health-related questionnaire outcomes when compared with SB through 5 years of follow-up. However, the EB is related to a higher number of reinterventions. Clinical Impact: This present study is the first to report five-year outcomes comparing an endoluminal (EB) using heparin-bonded self-expanding covered stents with surgical bypass (SB) for long and complex femoropopliteal disease. Although the advantages of treatment with EB are mostly seen in the early period after treatment, the outcomes support the use of EB for this indication and seems to be a valid and safe alternative for bypass surgery. Future trials comparing various endovascular strategies may provide further guidance for the development of an evidence-based treatment algorithm.</p

Observations of Particulates within the North Atlantic Flight Corridor: POLINAT 2, September-October 1997

This paper discusses particulate concentration and size distribution data gathered using the University of Missouri-Rolla Mobile Aerosol Sampling System (UMR-MASS), and used to investigate the southern extent of the eastern end of the North Atlantic Flight Corridor (NAFC) during project Pollution From Aircraft Emissions in the North Atlantic Flight Corridor/Subsonic Assessment (SASS) Ozone and Nitrogen Oxide Experiment (POLINAT 2/SONEX) from September 19 to October 23, 1997. The analysis presented in this paper focuses on the corridor effect, or enhancement of pollutants by jet aircraft combustion events. To investigate the phenomena, both vertical and horizontal profiles of the corridor, and regions immediately adjacent to the corridor, were performed. The profiles showed a time-dependent enhancement of particulates within the corridor, and a nonvolatile (with respect to thermal volatilization at 300° C) aerosol enhancement at corridor altitudes by a factor of 3.6. The southern extent of the North Atlantic Flight Corridor was established from a four flight average of the particulate data and yielded a boundary near 42.5° N during the study period. A size distribution analysis of the nonvolatile particulates revealed an enhancement in the \u3c40 nm particulates for size distributions recorded within the flight corridor