Knowledge Flows and Networks: the Interplay between Local and Global Linkages within Bangalore IT Cluster

This doctoral work gains deeper insight into the dynamics of knowledge flows within and across clusters, unfolding their features, directions and strategic implications. Alliances, networks and personnel mobility are acknowledged as the three main channels of inter-firm knowledge flows, thus offering three heterogeneous measures to analyze the phenomenon. The interplay between the three channels and the richness of available research methods, has allowed for the elaboration of three different papers and perspectives. The common empirical setting is the IT cluster in Bangalore, for its distinguished features as a high-tech cluster and for its steady yearly two-digit growth around the service-based business model. The first paper deploys both a firm-level and a tie-level analysis, exploring the cases of 4 domestic companies and of 2 MNCs active the cluster, according to a cluster-based perspective. The distinction between business-domain knowledge and technical knowledge emerges from the qualitative evidence, further confirmed by quantitative analyses at tie-level. At firm-level, the specialization degree seems to be influencing the kind of knowledge shared, while at tie-level both the frequency of interaction and the governance mode prove to determine differences in the distribution of knowledge flows. The second paper zooms out and considers the inter-firm networks; particularly focusing on the role of cluster boundary, internal and external networks are analyzed, in their size, long-term orientation and exploration degree. The research method is purely qualitative and allows for the observation of the evolving strategic role of internal network: from exploitation-based to exploration-based. Moreover, a causal pattern is emphasized, linking the evolution and features of the external network to the evolution and features of internal network. The final paper addresses the softer and more micro-level side of knowledge flows: personnel mobility. A social capital perspective is here developed, which considers both employees’ acquisition and employees’ loss as building inter-firm ties, thus enhancing company’s overall social capital. Negative binomial regression analyses at dyad-level test the significant impact of cluster affiliation (cluster firms vs non-cluster firms), industry affiliation (IT firms vs non-IT fims) and foreign affiliation (MNCs vs domestic firms) in shaping the uneven distribution of personnel mobility, and thus of knowledge flows, among companies.

Business Clusters in Eastern Europe: Policy Analysis and Cluster Performance

Clusters have increasingly become an essential part of policy discourses at all levels, EU, national, regional, dealing with regional development, competitiveness, innovation, entrepreneurship, SMEs. These impressive efforts in promoting the concept of clusters on the policy-making arena have been accompanied by much less academic and scientific research work investigating the actual economic performance of firms in clusters, the design and execution of cluster policies and going beyond singular case studies to a more methodologically integrated and comparative approach to the study of clusters and their real-world impact. The theoretical background is far from being consolidated and there is a variety of methodologies and approaches for studying and interpreting this phenomenon while at the same time little comparability among studies on actual cluster performances. The conceptual framework of clustering suggests that they affect performance but theory makes little prediction as to the ultimate distribution of the value being created by clusters. This thesis takes the case of Eastern European countries for two reasons. One is that clusters, as coopetitive environments, are a new phenomenon as the previous centrally-based system did not allow for such types of firm organizations. The other is that, as new EU member states, they have been subject to the increased popularization of the cluster policy approach by the European Commission, especially in the framework of the National Reform Programmes related to the Lisbon objectives. The originality of the work lays in the fact that starting from an overview of theoretical contributions on clustering, it offers a comparative empirical study of clusters in transition countries. There have been very few examples in the literature that attempt to examine cluster performance in a comparative cross-country perspective. It adds to this an analysis of cluster policies and their implementation or lack of such as a way to analyse the way the cluster concept has been introduced to transition economies. Our findings show that the implementation of cluster policies does vary across countries with some countries which have embraced it more than others. The specific modes of implementation, however, are very similar, based mostly on soft measures such as funding for cluster initiatives, usually directed towards the creation of cluster management structures or cluster facilitators. They are essentially founded on a common assumption that the added values of clusters is in the creation of linkages among firms, human capital, skills and knowledge at the local level, most often perceived as the regional level. Often times geographical proximity is not a necessary element in the application process and cluster application are very similar to network membership. Cluster mapping is rarely a factor in the selection of cluster initiatives for funding and the relative question about critical mass and expected outcomes is not considered. In fact, monitoring and evaluation are not elements of the cluster policy cycle which have received a lot of attention. Bulgaria and the Czech Republic are the countries which have implemented cluster policies most decisively, Hungary and Poland have made significant efforts, while Slovakia and Romania have only sporadically and not systematically used cluster initiatives. When examining whether, in fact, firms located within regional clusters perform better and are more efficient than similar firms outside clusters, we do find positive results across countries and across sectors. The only country with negative impact from being located in a cluster is the Czech Republic.

Cluster-derived Gold/Iron catalysts for environmental applications

During the last years we assisted to an exponential growth of scientific discoveries for catalysis by gold and many applications have been found for Au-based catalysts. In the literature there are several studies concerning the use of gold-based catalysts for environmental applications and good results are reported for the catalytic combustion of different volatile organic compounds (VOCs). Recently it has also been established that gold-based catalysts are potentially capable of being effectively employed in fuel cells in order to remove CO traces by preferential CO oxidation in H2-rich streams. Bi-metallic catalysts have attracted increasing attention because of their markedly different properties from either of the costituent metals, and above all their enhanced catalytic activity, selectivity and stability. In the literature there are several studies demostrating the beneficial effect due to the addition of an iron component to gold supported catalysts in terms of enhanced activity, selectivity, resistence to deactivation and prolonged lifetime of the catalyst. In this work we tried to develop a methodology for the preparation of iron stabilized gold nanoparticles with controlled size and composition, particularly in terms of obtaining an intimate contact between different phases, since it is well known that the catalytic behaviour of multi-component supported catalysts is strongly influenced by the size of the metal particles and by their reciprocal interaction. Ligand stabilized metal clusters, with nanometric dimensions, are possible precursors for the preparation of catalytically active nanoparticles with controlled dimensions and compositions. Among these, metal carbonyl clusters are quite attractive, since they can be prepared with several different sizes and compositions and, moreover, they are decomposed under very mild conditions. A novel preparation method was developed during this thesis for the preparation of iron and gold/iron supported catalysts using bi-metallic carbonyl clusters as precursors of highly dispersed nanoparticles over TiO2 and CeO2, which are widely considered two of the most suitable supports for gold nanoparticles. Au/FeOx catalysts were prepared by employing the bi-metallic carbonyl cluster salts [NEt4]4[Au4Fe4(CO)16] (Fe/Au=1) and [NEt4][AuFe4(CO)16] (Fe/Au=4), and for comparison FeOx samples were prepared by employing the homometallic [NEt4][HFe3(CO)11] cluster. These clusters were prepared by Prof. Longoni research group (Department of Physical and Inorganic Chemistry- University of Bologna). Particular attention was dedicated to the optimization of a suitable thermal treatment in order to achieve, apart from a good Au and Fe metal dispersion, also the formation of appropriate species with good catalytic properties. A deep IR study was carried out in order to understand the physical interaction between clusters and different supports and detect the occurrence of chemical reactions between them at any stage of the preparation. The characterization by BET, XRD, TEM, H2-TPR, ICP-AES and XPS was performed in order to investigate the catalysts properties, whit particular attention to the interaction between Au and Fe and its influence on the catalytic activity. This novel preparation method resulted in small gold metallic nanoparticles surrounded by highly dispersed iron oxide species, essentially in an amorphous phase, on both TiO2 and CeO2. The results presented in this thesis confirmed that FeOx species can stabilize small Au particles, since keeping costant the gold content but introducing a higher iron amount a higher metal dispersion was achieved. Partial encapsulation of gold atoms by iron species was observed since the Au/Fe surface ratio was found much lower than bulk ratio and a strong interaction between gold and oxide species, both of iron oxide and supports, was achieved. The prepared catalysts were tested in the total oxidation of VOCs, using toluene and methanol as probe molecules for aromatics and alchols, respectively, and in the PROX reaction. Different performances were observed on titania and ceria catalysts, on both toluene and methanol combustion. Toluene combustion on titania catalyst was found to be enhanced increasing iron loading while a moderate effect on FeOx-Ti activity was achieved by Au addition. In this case toluene combustion was improved due to a higher oxygen mobility depending on enhanced oxygen activation by FeOx and Au/FeOx dispersed on titania. On the contrary ceria activity was strongly decreased in the presence of FeOx, while the introduction of gold was found to moderate the detrimental effect of iron species. In fact, excellent ceria performances are due to its ability to adsorb toluene and O2. Since toluene activation is the determining factor for its oxidation, the partial coverage of ceria sites, responsible of toluene adsorption, by FeOx species finely dispersed on the surface resulted in worse efficiency in toluene combustion. Better results were obtained for both ceria and titania catalysts on methanol total oxidation. In this case, the performances achieved on differently supported catalysts indicate that the oxygen mobility is the determining factor in this reaction. The introduction of gold on both TiO2 and CeO2 catalysts, lead to a higher oxygen mobility due to the weakening of both Fe-O and Ce-O bonds and consequently to enhanced methanol combustion. The catalytic activity was found to strongly depend on oxygen mobility and followed the same trend observed for catalysts reducibility. Regarding CO PROX reaction, it was observed that Au/FeOx titania catalysts are less active than ceria ones, due to the lower reducibility of titania compared to ceria. In fact the availability of lattice oxygen involved in PROX reaction is much higher in the latter catalysts. However, the CO PROX performances observed for ceria catalysts are not really high compared to data reported in literature, probably due to the very low Au/Fe surface ratio achieved with this preparation method. CO preferential oxidation was found to strongly depend on Au particle size but also on surface oxygen reducibility, depending on the different oxide species which can be formed using different thermal treatment conditions or varying the iron loading over the support.

Researches on berry composition in red grape: agronomical, biochemical and molecular approaches

It is well known that the best grape quality can occur only through the achievement of optimal source/sink ratio. Vine balance is in fact a key parameter in controlling berry sugar, acidity and secondary metabolites content (Howell, 2001; Vanden Heuvel et al., 2004). Despite yield reduction and quality improvement are not always strictly related, cluster thinning is considered a technique which could lead to improvement in grape sugar and anthocyanin composition (Dokoozlian and Hirschfelt, 1995; Guidoni et al., 2002). Among several microclimatic variables which may impact grape composition, the effect of cluster light exposure and temperature, which probably act in synergistic and complex way, has been widely explored showing positive even sometimes contradictory results (Spayd et al., 2001; Tarara et al., 2008). Pre-bloom and véraison defoliation are very efficient techniques in inducing cluster microclimatic modification. Furthermore pre-bloom defoliation inducing a lower berry set percentage On these basis the aim of the first experiment of the thesis was to verify in cv Sangiovese the effects on ripening and berry composition of management techniques which may increase source/sink ratio and /or promote light incidence on berries throughout grape ripening. An integrated agronomic, biochemical and microarray approach, aims to understand which mechanisms are involved in berry composition and may be conditioned in the berries during ripening in vines submitted to three treatments. In particular the treatments compared were: a) cluster thinning (increasing in source/sink ratio) b) leaf removal at véraison (increasing cluster light exposure) c) pre-bloom defoliation (increasing source sink ratio and cluster light exposure). Vine response to leaf removal at véraison was further evaluated in the second experiment on three different varieties (Cabernet Sauvignon, Nero d’Avola, Raboso Piave) chosen for their different genetic traits in terms of anthocyanin amount and composition. The integrated agronomic, biochemical and microarray approach, employed in order to understand those mechanisms involved in berry composition of Sangiovese vines submitted to management techniques which may increase source/sink ratio and induce microclimatic changes, bring to interesting results. This research confirmed the main role of source/sink ratio in conditioning sugars metabolism and revealed also that carbohydrates availability is a crucial issue in triggering anthocyanin biosynthesis. More complex is the situation of pre-bloom defoliation, where source/sink and cluster light increase effects are associated to determine final berry composition. It results that the application of pre-bloom defoliation may be risky, as too much dependent on seasonal conditions (rain and temperature) and physiological vine response (leaf area recovery, photosynthetic compensation, laterals regrowth). Early induced stress conditions could bring cluster at véraison in disadvantage to trigger optimal berry ripening processes compared to untreated vines. This conditions could be maintained until harvest, if no previously described physiological recovery occurs. Certainly, light exposure increase linked to defoliation treatments, showed a positive and solid effect on flavonol biosynthesis, as in our conditions temperature was not so different among treatments. Except the last aspects, that could be confirmed also for véraison defoliation, microclimatic changes by themselves seemed not able to induce any modification in berry composition. Further studies are necessary to understand if the peculiar anthocyanic and flavonols composition detected in véraison defoliation could play important role in both color intensity and stability of wines.

The impact of R&D in firm value across Europe

In this thesis the impact of R&D expenditures on firm market value and stock returns is examined. This is performed in a sample of European listed firms for the period 2000-2009. I apply different linear and GMM econometric estimations for testing the impact of R&D on market prices and construct country portfolios based on firms’ R&D expenditure to market capitalization ratio for studying the effect of R&D on stock returns. The results confirm that more innovative firms have a better market valuation,investors consider R&D as an asset that produces long-term benefits for corporations. The impact of R&D on firm value differs across countries. It is significantly modulated by the financial and legal environment where firms operate. Other firm and industry characteristics seem to play a determinant role when investors value R&D. First, only larger firms with lower financial leverage that operate in highly innovative sectors decide to disclose their R&D investment. Second, the markets assign a premium to small firms, which operate in hi-tech sectors compared to larger enterprises for low-tech industries. On the other hand, I provide empirical evidence indicating that generally highly R&D-intensive firms may enhance mispricing problems related to firm valuation. As R&D contributes to the estimation of future stock returns, portfolios that comprise high R&D-intensive stocks may earn significant excess returns compared to the less innovative after controlling for size and book-to-market risk. Further, the most innovative firms are generally more risky in terms of stock volatility but not systematically more risky than low-tech firms. Firms that operate in Continental Europe suffer more mispricing compared to Anglo-Saxon peers but the former are less volatile, other things being equal. The sectors where firms operate are determinant even for the impact of R&D on stock returns; this effect is much stronger in hi-tech industries.

The impact of ice crystals on radiative forcing and remote sensing of arctic boundary-layer mixed-phase clouds

This PhD thesis is embedded into the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) and investigates the radiative transfer through Arctic boundary-layer mixed-phase (ABM) clouds. For this purpose airborne spectral solar radiation measurements and simulations of the solar and thermal infrared radiative transfer have been performed. This work reports on measurements with the Spectral Modular Airborne Radiation measurement sysTem (SMART-Albedometer) conducted in the framework of ASTAR in April 2007 close to Svalbard. For ASTAR the SMART-Albedometer was extended to measure spectral radiance. The development and calibration of the radiance measurements are described in this work. In combination with in situ measurements of cloud particle properties provided by the Laboratoire de M¶et¶eorologie Physique (LaMP) and simultaneous airborne lidar measurements by the Alfred Wegener Institute for Polar and Marine Research (AWI) ABM clouds were sampled. The SMART-Albedometer measurements were used to retrieve the cloud thermodynamic phase by three different approaches. A comparison of these results with the in situ and lidar measurements is presented in two case studies. Beside the dominating mixed-phase clouds pure ice clouds were found in cloud gaps and at the edge of a large cloud field. Furthermore the vertical distribution of ice crystals within ABM clouds was investigated. It was found that ice crystals at cloud top are necessary to describe the observed SMART-Albedometer measurements. The impact of ice crystals on the radiative forcing of ABM clouds is in vestigated by extensive radiative transfer simulations. The solar and net radiative forcing was found to depend on the ice crystal size, shape and the mixing ratio of ice crystals and liquid water droplets.

Global simulated soil biogenic nitric oxide (NO) emissions: Impact, improvement and innovation

rnNitric oxide (NO) is important for several chemical processes in the atmosphere. Together with nitrogen dioxide (NO2 ) it is better known as nitrogen oxide (NOx ). NOx is crucial for the production and destruction of ozone. In several reactions it catalyzes the oxidation of methane and volatile organic compounds (VOCs) and in this context it is involved in the cycling of the hydroxyl radical (OH). OH is a reactive radical, capable of oxidizing most organic species. Therefore, OH is also called the “detergent” of the atmosphere. Nitric oxide originates from several sources: fossil fuel combustion, biomass burning, lightning and soils. Fossil fuel combustion is the largest source. The others are, depending on the reviewed literature, generally comparable to each other. The individual sources show a different temporal and spatial pattern in their magnitude of emission. Fossil fuel combustion is important in densely populated places, where NO from other sources is less important. In contrast NO emissions from soils (hereafter SNOx) or biomass burning are the dominant source of NOx in remote regions.rnBy applying an atmospheric chemistry global climate model (AC-GCM) I demonstrate that SNOx is responsible for a significant part of NOx in the atmosphere. Furthermore, it increases the O3 and OH mixing ratio substantially, leading to a ∼10% increase in the oxidizing efficiency of the atmosphere. Interestingly, through reduced O3 and OH mixing ratios in simulations without SNOx, the lifetime of NOx increases in regions with other dominating sources of NOx

Unraveling efficiency-limiting processes in organic solar cells by ultrafast spectroscopy - impact of chemical structure and morphology on photophysics and efficiency

Diese Arbeit widmet sich der Untersuchung der photophysikalischen Prozesse, die in Mischungen von Elektronendonoren mit Elektronenakzeptoren zur Anwendung in organischen Solarzellen auftreten. Als Elektronendonoren werden das Copolymer PBDTTT-C, das aus Benzodithiophen- und Thienothiophene-Einheiten besteht, und das kleine Molekül p-DTS(FBTTh2)2, welches Silizium-überbrücktes Dithiophen, sowie fluoriertes Benzothiadiazol und Dithiophen beinhaltet, verwendet. Als Elektronenakzeptor finden ein planares 3,4:9,10-Perylentetracarbonsäurediimid-(PDI)-Derivat und verschiedene Fullerenderivate Anwendung. PDI-Derivate gelten als vielversprechende Alternativen zu Fullerenen aufgrund der durch chemische Synthese abstimmbaren strukturellen, optischen und elektronischen Eigenschaften. Das gewichtigste Argument für PDI-Derivate ist deren Absorption im sichtbaren Bereich des Sonnenspektrums was den Photostrom verbessern kann. Fulleren-basierte Mischungen übertreffen jedoch für gewöhnlich die Effizienz von Donor-PDI-Mischungen.rnUm den Nachteil der PDI-basierten Mischungen im Vergleich zu den entsprechenden Fulleren-basierten Mischungen zu identifizieren, werden die verschiedenen Donor-Akzeptor-Kombinationen auf ihre optischen, elektronischen und strukturellen Eigenschaften untersucht. Zeitaufgelöste Spektroskopie, vor allem transiente Absorptionsspektroskopie (TA), wird zur Analyse der Ladungsgeneration angewendet und der Vergleich der Donor-PDI Mischfilme mit den Donor-Fulleren Mischfilmen zeigt, dass die Bildung von Ladungstransferzuständen einen der Hauptverlustkanäle darstellt.rnWeiterhin werden Mischungen aus PBDTTT-C und [6,6]-Phenyl-C61-buttersäuremethylesther (PC61BM) mittels TA-Spektroskopie auf einer Zeitskala von ps bis µs untersucht und es kann gezeigt werden, dass der Triplettzustand des Polymers über die nicht-geminale Rekombination freier Ladungen auf einer sub-ns Zeitskala bevölkert wird. Hochentwickelte Methoden zur Datenanalyse, wie multivariate curve resolution (MCR), werden angewendet um überlagernde Datensignale zu trennen. Zusätzlich kann die Regeneration von Ladungsträgern durch Triplett-Triplett-Annihilation auf einer ns-µs Zeitskala gezeigt werden. Darüber hinaus wird der Einfluss des Lösungsmitteladditivs 1,8-Diiodooctan (DIO) auf die Leistungsfähigkeit von p-DTS(FBTTh2)2:PDI Solarzellen untersucht. Die Erkenntnisse von morphologischen und photophysikalischen Experimenten werden kombiniert, um die strukturellen Eigenschaften und die Photophysik mit den relevanten Kenngrößen des Bauteils in Verbindung zu setzen. Zeitaufgelöste Photolumineszenzmessungen (time-resolved photoluminescence, TRPL) zeigen, dass der Einsatz von DIO zu einer geringeren Reduzierung der Photolumineszenz führt, was auf eine größere Phasentrennung zurückgeführt werden kann. Außerdem kann mittels TA Spektroskopie gezeigt werden, dass die Verwendung von DIO zu einer verbesserten Kristallinität der aktiven Schicht führt und die Generation freier Ladungen fördert. Zur genauen Analyse des Signalzerfalls wird ein Modell angewendet, das den gleichzeitigen Zerfall gebundener CT-Zustände und freier Ladungen berücksichtigt und optimierte Donor-Akzeptor-Mischungen zeigen einen größeren Anteil an nicht-geminaler Rekombination freier Ladungsträger.rnIn einer weiteren Fallstudie wird der Einfluss des Fullerenderivats, namentlich IC60BA und PC71BM, auf die Leistungsfähigkeit und Photophysik der Solarzellen untersucht. Eine Kombination aus einer Untersuchung der Struktur des Dünnfilms sowie zeitaufgelöster Spektroskopie ergibt, dass Mischungen, die ICBA als Elektronenakzeptor verwenden, eine schlechtere Trennung von Ladungstransferzuständen zeigen und unter einer stärkeren geminalen Rekombination im Vergleich zu PCBM-basierten Mischungen leiden. Dies kann auf die kleinere Triebkraft zur Ladungstrennung sowie auf die höhere Unordnung der ICBA-basierten Mischungen, die die Ladungstrennung hemmen, zurückgeführt werden. Außerdem wird der Einfluss reiner Fullerendomänen auf die Funktionsfähigkeit organischer Solarzellen, die aus Mischungen des Thienothienophen-basierenden Polymers pBTTT-C14 und PC61BM bestehen, untersucht. Aus diesem Grund wird die Photophysik von Filmen mit einem Donor-Akzeptor-Mischungsverhältnis von 1:1 sowie 1:4 verglichen. Während 1:1-Mischungen lediglich eine co-kristalline Phase, in der Fullerene zwischen den Seitenketten von pBTTT interkalieren, zeigen, resultiert der Überschuss an Fulleren in den 1:4-Proben in der Ausbildung reiner Fullerendomänen zusätzlich zu der co kristallinen Phase. Transiente Absorptionsspektroskopie verdeutlicht, dass Ladungstransferzustände in 1:1-Mischungen hauptsächlich über geminale Rekombination zerfallen, während in 1:4 Mischungen ein beträchtlicher Anteil an Ladungen ihre wechselseitige Coulombanziehung überwinden und freie Ladungsträger bilden kann, die schließlich nicht-geminal rekombinieren.

Ventilation-perfusion ratio in perflubron during partial liquid ventilation

BACKGROUND: Functional magnetic resonance imaging (fMRI) of fluorine-19 allows for the mapping of oxygen partial pressure within perfluorocarbons in the alveolar space (Pao(2)). Theoretically, fMRI-detected Pao(2) can be combined with the Fick principle approach, i.e., a mass balance of oxygen uptake by ventilation and delivery by perfusion, to quantify the ventilation-perfusion ratio (Va/Q) of a lung region: The mixed venous blood and the inspiratory oxygen fraction, which are equal for all lung regions, are measured. In addition, the local expiratory oxygen fraction and the end capillary oxygen content, both of which may differ between the lung regions, are calculated using the fMRI-detected Pao(2). We investigated this approach by numerical simulations and applied it to quantify local Va/Q in the perfluorocarbons during partial liquid ventilation. METHODS: Numerical simulations were performed to analyze the sensitivity of the Va/Q calculation and to compare this approach with another one proposed by Rizi et al. in 2004 (Magn Reson Med 2004;52:65-72). Experimentally, the method was used during partial liquid ventilation in 7 anesthetized pigs. The Pao(2) distribution in intraalveolar perflubron was measured by fluorine-19 MRI. Respiratory gas fractions together with arterial and mixed venous blood samples were taken to quantify oxygen partial pressure and content. Using the Fick principle, the local Va/Q was estimated. The impact of gravity (nondependent versus dependent) of perflubron dose (10 vs 20 mL/kg body weight) and of inspired oxygen fraction (Fio(2)) (0.4-1.0) on Va/Q was examined. RESULTS: In numerical simulations, the Fick principle proved to be appropriate over the Va/Q range from 0.02 to 2.5. Va/Q values were in acceptable agreement with the method published by Rizi et al. In the experimental setting, low mean Va/Q values were found in perflubron (confidence interval [CI] 0.08-0.29 with 20 mL/kg perflubron). At this dose, Va/Q in the nondependent lung was higher (CI 0.18-0.39) than in the dependent lung regions (CI 0.06-0.16; P = 0.006; Student t test). Differences depending on Fio(2) or perflubron dose were, however, small. CONCLUSION: The results show that derivation of Va/Q from local Po(2) measurements using fMRI in perflubron is feasible. The low detected Va/Q suggests that oxygen transport into the perflubron-filled alveolar space is significantly restrained.

The impact of body mass index on the one year outcomes of patients treated by percutaneous coronary intervention with Biolimus- and Sirolimus-eluting stents (from the LEADERS Trial)

The aim of this analysis was to assess the effect of body mass index (BMI) on 1-year outcomes in patients enrolled in a contemporary percutaneous coronary intervention trial comparing a sirolimus-eluting stent with a durable polymer to a biolimus-eluting stent with a biodegradable polymer. A total of 1,707 patients who underwent percutaneous coronary intervention were randomized to treatment with either biolimus-eluting stents (n = 857) or sirolimus-eluting stents (n = 850). Patients were assigned to 1 of 3 groups according to BMI: normal (<25 kg/m(2)), overweight (25 to 30 kg/m(2)), or obese (>30 kg/m(2)). At 1 year, the incidence of the composite of cardiac death, myocardial infarction, and clinically justified target vessel revascularization was assessed. In addition, rates of clinically justified target lesion revascularization and stent thrombosis were assessed. Cox proportional-hazards analysis, adjusted for clinical differences, was used to develop models for 1-year mortality. Forty-five percent of the patients (n = 770) were overweight, 26% (n = 434) were obese, and 29% (n = 497) had normal BMIs. At 1-year follow-up, the cumulative rate of cardiac death, myocardial infarction, and clinically justified target vessel revascularization was significantly higher in the obese group (8.7% in normal-weight, 11.3% in overweight, and 14.5% in obese patients, p = 0.01). BMI (hazard ratio 1.47, 95% confidence interval 1.02 to 2.14, p = 0.04) was an independent predictor of stent thrombosis. Stent type had no impact on the composite of cardiac death, myocardial infarction, and clinically justified target vessel revascularization at 1 year in the 3 BMI groups (hazard ratio 1.08, 95% confidence interval 0.63 to 1.83, p = 0.73). In conclusion, BMI was an independent predictor of major adverse cardiac events at 1-year clinical follow-up. The higher incidence of stent thrombosis in the obese group may suggest the need for a weight-adjusted dose of clopidogrel.

Impact of arterial injury on neointimal hyperplasia after implantation of drug-eluting stents in coronary arteries: an intravascular ultrasound study

Aims: We investigated the impact of arterial injury on neointimal hyperplasia following implantation of drug-eluting stents (DES). Methods and results: A total of 196 patients with 223 segments (sirolimus-eluting stents [SES]: 104, paclitaxel-eluting stents [PES]: 119) underwent intravascular ultrasound eight months after DES implantation. Arterial injury was defined as the balloon-to-artery ratio (BAR). Segments were categorised into two groups: high BAR defined as BAR>1.1 (120 segments), and low BAR defined as BAR ≤1.1 (103 segments). Baseline clinical characteristics were similar for both groups. Although reference vessel diameter was smaller, stent diameter, maximal balloon pressure and balloon diameter were higher in the high BAR compared with the low BAR group. Lumen (7.10±1.91 vs. 6.25±1.69, p=0.001), stent (7.31±1.95 vs. 6.41±1.80, p=0.001), and external elastic membrane (17.1±4.9 vs. 14.8±4.0, p<0.0001) areas (mm2) were higher, but neointimal hyperplasia (0.21±0.36 vs. 0.16±0.48, p=0.42) area (mm2) was similar in the high BAR compared with the low BAR group. Arterial injury as assessed by BAR was not associated with the amount of neointimal hyperplasia (R2=0.003, p=0.40). Conclusions: Arterial injury does not correlate with the amount of neointimal hyperplasia following DES implantation. Conventionally aggressive DES implantation techniques do not adversely affect long-term outcome with respect to restenosis. - See more at: http://www.pcronline.com/eurointervention/30th_issue/79/#sthash.1do4X31G.dpuf

Impact of treatment characteristics on response of different breast cancer phenotypes: pooled analysis of the German neo-adjuvant chemotherapy trials

Pathological complete response (pCR) to neoadjuvant treatment correlates with outcome in breast cancer. We determined whether characteristics of neoadjuvant therapy are associated with pCR. We used multi-level models, which accounted for heterogeneity in pCR across trials and trial arms, to analyze individual patient data from 3332 women included in 7 German neoadjuvant trials with uniform protocols. PCR was associated with an increase in number of chemotherapy cycles (odds ratio [OR] 1.2 for every two additional cycles; P = 0.009), with higher cumulative anthracycline doses (OR 1.6; P = 0.002), higher cumulative taxane doses (OR 1.6; P = 0.009), and with capecitabine containing regimens (OR 1.62; P = 0.022). Association of pCR with increase in number of cycles appeared more pronounced in hormone receptor (HR)-positive tumors (OR 1.35) than in HR-negative tumors (OR 1.04; P for interaction = 0.046). Effect of anthracycline dose was particularly pronounced in HER2-negative tumors (OR 1.61), compared to HER2-positive tumors (OR 0.83; P for interaction = 0.14). Simultaneous trastuzumab treatment in HER2-positive tumors increased odds of pCR 3.2-fold (P < 0.001). No association of pCR and number of trastuzumab cycles was found (OR 1.20, P = 0.39). Dosing characteristics appear important for successful treatment of breast cancer. Longer treatment, higher cumulative doses of anthracyclines and taxanes, and the addition of capecitabine and trastuzumab are associated with better response. Tailoring according to breast cancer phenotype might be possible: longer treatment in HR-positive tumors, higher cumulative anthracycline doses for HER2-negative tumors, shorter treatment at higher cumulative doses for triple-negative tumors, and limited number of preoperative trastuzumab cycles in HER2-positive tumors.

Impact of body mass index on the five-year outcome of patients having percutaneous coronary interventions with drug-eluting stents

The purpose of this study was to assess the impact of body mass index (BMI) on clinical outcome of patients treated by percutaneous coronary intervention (PCI) using drug-eluting stents. Patients were stratified according to BMI as normal (<25 kg/m(2)), overweight (25 to 30 kg/m(2)), or obese (>30 kg/m(2)). At 5-year follow-up all-cause death, myocardial infarction, clinically justified target vessel revascularization (TVR), and definite stent thrombosis were assessed. A complete dataset was available in 7,427 patients, of which 45%, 22%, and 33% were classified according to BMI as overweight, obese, and normal, respectively. Mean age of patients was significantly older in those with a normal BMI (p <0.05). Incidence of diabetes mellitus, hypertension, and dyslipidemia increased as BMI increased (p <0.05). Significantly higher rates of TVR (15.3% vs 12.8%, p = 0.02) and early stent thrombosis (1.5% vs 0.9%, p = 0.04) were observed in the obese compared to the normal BMI group. No significant difference among the 3 BMI groups was observed for the composite of death/myocardial infarction/TVR or for definite stent thrombosis at 5 years, whereas the normal BMI group was at higher risk for all-cause death at 5 years (obese vs normal BMI, hazard ratio 0.74, confidence interval 0.53 to 0.99, p = 0.05; overweight vs normal BMI, hazard ratio 0.73, confidence interval 0.59 to 0.94, p = 0.01) in the multivariate Cox proportional hazard model. Age resulted in a linearly dependent covariate with BMI in the all-cause 5-year mortality multivariate model (p = 0.001). In conclusion, the "obesity paradox" observed in 5-year all-cause mortality could be explained by the higher rate of elderly patients in the normal BMI group and the existence of colinearity between BMI and age. However, obese patients had a higher rate of TVR and early stent thrombosis and a higher rate of other risk factors such as diabetes mellitus, hypertension, and hypercholesterolemia.

Impact of measurement errors on the determination of the linear modulus of human meniscal attachments

For the development of meniscal substitutes and related finite element models it is necessary to know the mechanical properties of the meniscus and its attachments. Measurement errors can falsify the determination of material properties. Therefore the impact of metrological and geometrical measurement errors on the determination of the linear modulus of human meniscal attachments was investigated. After total differentiation the error of the force (+0.10%), attachment deformation (−0.16%), and fibre length (+0.11%) measurements almost annulled each other. The error of the cross-sectional area determination ranged from 0.00%, gathered from histological slides, up to 14.22%, obtained from digital calliper measurements. Hence, total measurement error ranged from +0.05% to −14.17%, predominantly affected by the cross-sectional area determination error. Further investigations revealed that the entire cross-section was significantly larger compared to the load-carrying collagen fibre area. This overestimation of the cross-section area led to an underestimation of the linear modulus of up to −36.7%. Additionally, the cross-sections of the collagen-fibre area of the attachments significantly varied up to +90% along their longitudinal axis. The resultant ratio between the collagen fibre area and the histologically determined cross-sectional area ranged between 0.61 for the posterolateral and 0.69 for the posteromedial ligament. The linear modulus of human meniscal attachments can be significantly underestimated due to the use of different methods and locations of cross-sectional area determination. Hence, it is suggested to assess the load carrying collagen fibre area histologically, or, alternatively, to use the correction factors proposed in this study.

Impact of admission glucose and diabetes on recanalization and outcome after intra-arterial thrombolysis for ischaemic stroke

BACKGROUND: Stroke patients with diabetes and admission hyperglycaemia have worse outcomes than non-diabetics, with or without intravenous thrombolysis. Poor vessel recanalization was reported in diabetics treated with intravenous thrombolysis. AIMS: This study aimed to determine the impact of admission glucose and diabetes on recanalization and outcome after intra-arterial thrombolysis. METHODS: We analysed 389 patients (213 men, 176 women) treated with intra-arterial thrombolysis. The association of diabetes and admission glucose value with recanalization, outcome, mortality, and symptomatic intracranial haemorrhage was determined. Recanalization was classified according to thrombolysis in myocardial infarction grades. Outcome was measured using the modified Rankin Scale at three-months and categorized as favourable (modified Rankin Scale 0-2) or poor (modified Rankin Scale 3-6). RESULTS: The rate of partial or complete recanalization (thrombolysis in myocardial infarction 2-3) did not differ between patients with and without diabetes (67% vs. 66%; P = 1·000). Mean admission glucose values were similar in patients with poor recanalization (thrombolysis in myocardial infarction 0-1) and patients with partial or complete recanalization (thrombolysis in myocardial infarction 2-3; 7·3 vs. 7·3 mmol/l; P = 0·746). Follow-up at three-months was obtained in 388 of 389 patients. Clinical outcome was favourable (modified Rankin Scale 0-2) in 189 patients (49%) and poor (modified Rankin Scale 3-6) in 199 patients (51%). Mortality at three-months was 20%. Diabetics were more likely to have poor outcome (72% vs. 48%; P = 0·001) and to be dead (30% vs. 19%; P = 0·044) at three-months. After multivariable analysis, there remained an independent relationship between diabetes and outcome (P = 0·003; odds ratio 3·033, 95% confidence interval 1·452-6·336), but not with mortality (P = 0·310; odds ratio 1·436; 95% confidence interval 0·714-2·888). Moreover, higher age (P = 0·001; odds ratio 1·039; 95% confidence interval 1·017-1·061), higher baseline National Institutes of Health Stroke Scale score (P < 0·0001; odds ratio 1·130; 95% confidence interval 1·079-1·182), location of vessel occlusion as categorical variable (P < 0·0001), poor collaterals (P = 0·02; odds ratio 1·587; 95% confidence interval 1·076-2·341), poor vessel recanalization (P < 0·0001; odds ratio 4·713; 95% confidence interval 2·627-8·454), and higher leucocyte count (P = 0·032; odds ratio 1·094; 95% confidence interval 1·008-1·188) were independent baseline predictors of poor outcome. Higher admission glucose was associated with poor outcome (P = 0·006) and mortality (P < 0·0001). After multivariate analyses, glucose remained independently associated with poor outcome (P = 0·019; odds ratio 1·150; 95% confidence interval 1·023-1-292) and mortality (P = 0·005; odds ratio 1·183; 95% confidence interval 1052-1·331). The rate of symptomatic intracranial haemorrhage was similar in diabetics and non-diabetics (6·7% vs. 4·6%; P = 0·512). Mean admission glucose was higher in patients with symptomatic intracranial haemorrhage than without (8·58 vs. 7·26 mmol/l; P = 0·010). Multivariable analysis confirmed an independent association between admission glucose and symptomatic intracranial haemorrhage (P = 0·027; odds ratio 1·187; 95% confidence interval 1·020-1·381). CONCLUSIONS: Diabetes and glucose value on admission did not influence recanalization after intra-arterial thrombolysis; nevertheless, they were independent predictors of poor outcome after intra-arterial thrombolysis and a higher admission glucose value was an independent predictor of symptomatic intracranial haemorrhage. This indicates that factors on the capillary, cellular, or metabolic level may account for the worse outcome in patients with elevated glucose value and diabetes.