Showing papers by "University of Patras published in 2009"
TL;DR: In this paper, the constitutive relation of graphene and probe the physics of its optical phonons by studying its Raman spectrum as a function of uniaxial strain was uncovered.
Abstract: We uncover the constitutive relation of graphene and probe the physics of its optical phonons by studying its Raman spectrum as a function of uniaxial strain. We find that the doubly degenerate E(2g) optical mode splits in two components: one polarized along the strain and the other perpendicular. This splits the G peak into two bands, which we call G(+) and G(-), by analogy with the effect of curvature on the nanotube G peak. Both peaks redshift with increasing strain and their splitting increases, in excellent agreement with first-principles calculations. Their relative intensities are found to depend on light polarization, which provides a useful tool to probe the graphene crystallographic orientation with respect to the strain. The 2D and 2D(') bands also redshift but do not split for small strains. We study the Gruneisen parameters for the phonons responsible for the G, D, and D(') peaks. These can be used to measure the amount of uniaxial or biaxial strain, providing a fundamental tool for nanoelectronics, where strain monitoring is of paramount importance.
1,762 citations
TL;DR: Investigation of the role of exogenous and endogenous hydrogen sulfide on neovascularization and wound healing in vitro and in vivo concludes that endogenous and exogenous H2S stimulates EC-related angiogenic properties through a KATP channel/MAPK pathway.
Abstract: The goal of the current study was to investigate the role of exogenous and endogenous hydrogen sulfide (H2S) on neovascularization and wound healing in vitro and in vivo Incubation of endothelial cells (ECs) with H2S enhanced their angiogenic potential, evidenced by accelerated cell growth, migration, and capillary morphogenesis on Matrigel Treatment of chicken chorioallantoic membranes (CAMS) with H2S increased vascular length Exposure of ECs to H2S resulted in increased phosphorylation of Akt, ERK, and p38 The KATP channel blocker glibenclamide or the p38 inhibitor SB203580 abolished H2S-induced EC motility Since glibenclamide inhibited H2S-triggered p38 phosphorylation, we propose that KATP channels lay upstream of p38 in this process When CAMs were treated with H2S biosynthesis inhibitors dl-propylargylglycine or beta-cyano-L-alanine, a reduction in vessel length and branching was observed, indicating that H2S serves as an endogenous stimulator of the angiogenic response Stimulation of ECs with vascular endothelial growth factor (VEGF) increased H2S release, while pharmacological inhibition of H2S production or KATP channels or silencing of cystathionine gamma-lyase (CSE) attenuated VEGF signaling and migration of ECs These results implicate endothelial H2S synthesis in the pro-angiogenic action of VEGF Aortic rings isolated from CSE knockout mice exhibited markedly reduced microvessel formation in response to VEGF when compared to wild-type littermates Finally, in vivo, topical administration of H2S enhanced wound healing in a rat model, while wound healing was delayed in CSE−/− mice We conclude that endogenous and exogenous H2S stimulates EC-related angiogenic properties through a KATP channel/MAPK pathway
753 citations
TL;DR: A computer‐assisted classification method combining conventional MRI and perfusion MRI is developed and used for differential diagnosis and consists of several steps including region‐of‐interest definition, feature extraction, feature selection, and classification.
Abstract: The objective of this study is to investigate the use of pattern classification methods for distinguishing different types of brain tumors, such as primary gliomas from metastases, and also for grading of gliomas. The availability of an automated computer analysis tool that is more objective than human readers can potentially lead to more reliable and reproducible brain tumor diagnostic procedures. A computer-assisted classification method combining conventional MRI and perfusion MRI is developed and used for differential diagnosis. The proposed scheme consists of several steps including ROI definition, feature extraction, feature selection and classification. The extracted features include tumor shape and intensity characteristics as well as rotation invariant texture features. Feature subset selection is performed using Support Vector Machines (SVMs) with recursive feature elimination. The method was applied on a population of 102 brain tumors histologically diagnosed as metastasis (24), meningiomas (4), gliomas WHO grade 2 (22), gliomas WHO grade 3 (18), and glioblastomas (34). The binary SVM classification accuracy, sensitivity, and specificity, assessed by leave-one-out cross-validation, were respectively 85%, 87%, and 79% for discrimination of metastases from gliomas, and 88%, 85%, and 96% for discrimination of high grade (grade III and IV) from low grade (grade II) neoplasms. Multi-class classification was also performed via a one-versus-all voting scheme.
666 citations
Tokyo University of Agriculture and Technology1, University of Tokyo2, University of Hong Kong3, Universiti Putra Malaysia4, California Coastal Commission5, University of Aveiro6, Ehime University7, University of Patras8, Council of Scientific and Industrial Research9, California State University, Long Beach10, University of Plymouth11
TL;DR: The utility and feasibility of the International Pellet Watch approach to monitor POPs at a global scale are demonstrated and high concentrations of pesticide HCHs were detected in the pellets from southern Africa, suggesting current usage of the pesticides in southern Africa.
545 citations
TL;DR: In this paper, a cantilever-beam arrangement was used to examine the structural properties of graphene flakes under both tension and compression using two sets of samples, one consisting of flakes just supported on a plastic bar and the other consisting of flake embedded within the substrate.
Abstract: Themechanical behaviorof grapheneflakesunderboth tension and compression is examined using a cantilever-beam arrangement. Twodifferent sets of samples are employed.One consists of flakes just supported on a plastic bar. The other consists of flakesembeddedwithin theplastic substrate.Bymonitoring the shift of the 2DRaman linewith strain, information on the stress transfer efficiency as a function of stress sign and monolayer support are obtained. In tension, the embedded flake seems to sustain strains up to 1.3%, whereas in compression there is an indication of flake buckling at about 0.7% strain. The retainment of such a high critical buckling strain confirms the relative high flexural rigidity of the embedded monolayer. The mechanical strength and stiffness of crystalline materials are normally governed by the strength and stiffness
425 citations
TL;DR: In this article, the authors considered the non-relativistic Ho\v{r}ava-Lifshitz four-dimensional theory of gravity and showed that it has the same Newtonian and post-Newtonian limits as GR and thus, it passes the classical tests.
411 citations
TL;DR: The retainment of such a high critical buckling strain confirms the relative high flexural rigidity of the embedded monolayer.
Abstract: The mechanical behaviour of graphene flakes under both tension and compression is examined using a cantilever-beam arrangement. Two different sets of samples were employed involving flakes just supported on a plastic bar but also embedded within the plastic substrate. By monitoring the shift of the 2D Raman line with strain, information on the stress transfer efficiency as a function of stress sign and monolayer support were obtained. In tension, the embedded flake seems to sustain strains up to 1.3%, whereas in compression there is an indication of flake buckling at about 0.7% strain. The retainment of such a high critical buckling strain confirms the relative high flexural rigidity of the embedded monolayer.
397 citations
TL;DR: Under these exceptionally mild conditions 2-chlorotrityl cations generated during the cleavage of amino acids and peptides from resin do not attack the nucleophilic side chains of Trp, Met, and Tyr.
Abstract: The esterification of 2-chlorotrityl chloride resin with Fmoc-amino acids in the presence of DIEA is studied under various conditions. High esterification yields are obtained using 0.6 equiv. Fmoc-amino acid/mmol resin in DCM or DCE, in 25 min, at room temperature. The reaction proceeds without by product formation even in the case of Fmoc-Asn and Fmoc-Gln. The quantitative and easy cleavage of amino acids and peptides from 2-chlorotrityl resin, by using AcOH/TFE/DCM mixtures, is accomplished within 15-60 min at room temperature, while t-butyl type protecting groups remain unaffected. Under these exceptionally mild conditions 2-chlorotrityl cations generated during the cleavage of amino acids and peptides from resin do not attack the nucleophilic side chains of Trp, Met, and Tyr.
367 citations
TL;DR: Significant differences in the process of lipid accumulation as related to the carbon sources used were observed for both microorganisms, and the growth of both C. echinulata and M. isabellina on raw glycerol resulted in lower yields in terms of both biomass and oil produced than the growth on xylose.
Abstract: The biochemical behavior (biomass production, accumulation of total lipid, substrate uptake, fatty acid composition of fungal oil) of two oleaginous Mucorales strains, namely Mortierella isabellina ATHUM 2935 and Cunninghamella echinulata ATHUM 4411, was studied when the aforementioned microorganisms were cultivated on xylose, raw glycerol and glucose under nitrogen-limited conditions. Significant differences in the process of lipid accumulation as related to the carbon sources used were observed for both microorganisms. These differences were attributed to the different metabolic pathways involved in the assimilation of the above substrates. Therefore, the various carbon sources were channeled, at different extent, to storage lipid or to lipid-free biomass formation. Although glucose containing media favored the production of mycelial mass (15 g L −1 of total biomass in the case of C. echinulata and 27 g L −1 in the case of M. isabellina ), the accumulated lipid in dry matter was 46.0% for C. echinulata and 44.6% for M. isabellina . Lipid accumulation was induced on xylose containing media ( M. isabellina accumulated 65.5% and C. echinulata 57.7% of lipid, wt wt −1 , in dry mycelial mass). In these conditions, lipids of C. echinulata contained significant quantities of γ -linolenic acid (GLA). This fungus, when cultivated on xylose, produced 6.7 g L −1 of single cell oil and 1119 mg L −1 of GLA. Finally, the growth of both C. echinulata and M. isabellina on raw glycerol resulted in lower yields in terms of both biomass and oil produced than the growth on xylose.
311 citations
Harish-Chandra Research Institute1, Boston University2, CERN3, Columbia University4, Durham University5, Fermilab6, University of Paris-Sud7, Technische Universität München8, University of Geneva9, Max Planck Society10, Imperial College London11, Iowa State University12, University of California, Irvine13, Joint Institute for Nuclear Research14, University of Jyväskylä15, University of Kansas16, KEK17, University of Groningen18, Lawrence Berkeley National Laboratory19, Instituto Superior Técnico20, Los Alamos National Laboratory21, Lyon College22, Autonomous University of Madrid23, Tata Institute of Fundamental Research24, Northern Illinois University25, Northwestern University26, Osaka University27, University of Patras28, University of Pennsylvania29, Pontifical Catholic University of Rio de Janeiro30, Sapienza University of Rome31, Pontifical Catholic University of Chile32, University of Southampton33, University of Sussex34, National Cheng Kung University35, Technion – Israel Institute of Technology36, Tohoku University37, University of Tokyo38, Institute for the Physics and Mathematics of the Universe39, University of California, Berkeley40, Tokyo Metropolitan University41, International School for Advanced Studies42, University of Trieste43, International Centre for Theoretical Physics44, Spanish National Research Council45, University of Warwick46, University of Washington47, College of William & Mary48, University of Wisconsin-Madison49, University of Würzburg50, ETH Zurich51, University of Zurich52
TL;DR: The conclusions of the Physics Working Group of the International Scoping Study of a future Neutrino Factory and super-beam facility (the ISS) are presented in this article.
Abstract: The conclusions of the Physics Working Group of the International Scoping Study of a future Neutrino Factory and super-beam facility (the ISS) are presented. The ISS was carried out by the international community between NuFact05, (the 7th International Workshop on Neutrino Factories and Super-beams, Laboratori Nazionali di Frascati, Rome, 21–26 June 2005) and NuFact06 (Ivine, CA, 24–30 August 2006). The physics case for an extensive experimental programme to understand the properties of the neutrino is presented and the role of high-precision measurements of neutrino oscillations within this programme is discussed in detail. The performance of second-generation super-beam experiments, beta-beam facilities and the Neutrino Factory are evaluated and a quantitative comparison of the discovery potential of the three classes of facility is presented. High-precision studies of the properties of the muon are complementary to the study of neutrino oscillations. The Neutrino Factory has the potential to provide extremely intense muon beams and the physics potential of such beams is discussed in the final section of the report.
290 citations
TL;DR: In this article, the thermal stability of thin PEDOT:PSS films was investigated by dc conductivity measurements, X-ray and UV photoelectron spectroscopies as a function of heating temperature and heating time.
TL;DR: In this article, the authors present a simple and effective method for the inelastic displacement ratio estimation of a structure under repeated or multiple earthquakes, in terms of the period of vibration, the viscous damping ratio, the strain-hardening ratio, force reduction factor and the soil class.
01 May 2009
TL;DR: Digital manufacturing has been considered, over the last decade, as a highly promising set of technologies for reducing product development times and cost as well as for addressing the need of addressing the issues in manufacturing as discussed by the authors.
Abstract: Digital manufacturing has been considered, over the last decade, as a highly promising set of technologies for reducing product development times and cost as well as for addressing the need...
TL;DR: Pooled analyses suggest that MET with alpha-blockers or calcium channel blockers augments stone expulsion rates, reduces the time to stone expulsion, and lowers analgesia requirements for ureteral stones with and without ESWL for stones < or = 10 mm.
TL;DR: In this article, a techno-economic analysis of a process that produces biodiesel from vegetable oils is presented with the aim to investigate the dependence of the critical profitability indicators on the production capacity.
Doğuş University1, CERN2, Russian Academy of Sciences3, University of Alberta4, University of Zaragoza5, University of Glasgow6, Hellenic Open University7, Max Planck Society8, University of Chicago9, Aristotle University of Thessaloniki10, University of Freiburg11, University of British Columbia12, Ruhr University Bochum13, Technische Universität Darmstadt14, Goethe University Frankfurt15, Karlsruhe Institute of Technology16, Fermilab17, Lawrence Livermore National Laboratory18, University of Patras19, Brookhaven National Laboratory20
TL;DR: In this paper, the authors reported results from CAST with evacuated magnet bores (phase I), setting limits on lower mass axions, and they also reported results of CAST Phase II, where the magnetbores were filled with 4He gas (phase II) of variable pressure.
Abstract: We have searched for solar axions or other pseudoscalar particles that couple to two photons by using the CERN Axion Solar Telescope (CAST) setup. Whereas we previously have reported results from CAST with evacuated magnet bores (Phase I), setting limits on lower mass axions, here we report results from CAST where the magnet bores were filled with 4He gas (Phase II) of variable pressure. The introduction of gas generates a refractive photon mass mγ, thereby achieving the maximum possible conversion rate for those axion masses ma that match mγ. With 160 different pressure settings we have scanned ma up to about 0.4 eV, taking approximately 2 h of data for each setting. From the absence of excess x-rays when the magnet was pointing to the Sun, we set a typical upper limit on the axion-photon coupling of gaγ2.2 × 10−10 GeV−1 at 95% CL for ma0.4 eV, the exact result depending on the pressure setting. The excluded parameter range covers realistic axion models with a Peccei-Quinn scale in the neighborhood of fa ~ 107 GeV. Currently in the second part of CAST Phase II, we are searching for axions with masses up to about 1.2 eV using 3He as a buffer gas.
TL;DR: In this paper, the authors reflect on the evolution of accident causation models and accident investigation methods over time, revealing a gradual shift from searching for a single immediate cause, to the recognition of multiple causes.
TL;DR: The significant cognitive enhancement observed in adult mice after short-term i.p. supplementation with the blueberry extract concentrated in polyphenols, is closely related to higher brain antioxidant properties and inhibition of AChE activity.
TL;DR: After controlling for BMI-related effects, adiponectin levels seem to be lower in women with PCOS compared with non-PCOS controls, and low levels of adiponECTin in PCOS are probably related to IR but not to testosterone.
Abstract: results: Women with PCOS demonstrated significantly lower adiponectin values (weighted mean difference (95% confidence interval) 21.71 (22.82 to 20.6), P , 10 24 ), yet with significant between-study heterogeneity. Lower adiponectin levels are associated with the IR observed in women with PCOS, compared with controls. IR, but not total testosterone, was found significant among biological parameters explored in the meta-regression model. Hypoadiponectinaemia was present in both lean and obese women with PCOS when compared with non-PCOS counterparts. Data on high molecular weight (HMW) adiponectin are limited (three studies). conclusions: After controlling for BMI-related effects, adiponectin levels seem to be lower in women with PCOS compared with non- PCOS controls. Low levels of adiponectin in PCOS are probably related to IR but not to testosterone. Total adiponectin should not be used as a biomarker of PCOS severity. Further investigation is needed for HMW adiponectin levels in PCOS.
TL;DR: An interdisciplinary summary of the current body of knowledge on autumn colours is provided, and unresolved issues and future avenues of research are discussed that might help reveal the evolutionary meaning of this spectacle of nature.
Abstract: Leaf colour change is commonly observed in temperate deciduous forests in autumn. This is not simply a side effect of leaf senescence, and, in the past decade, several hypotheses have emerged to explain the evolution of autumn colours. Yet a lack of crosstalk between plant physiologists and evolutionary ecologists has resulted in slow progress, and so the adaptive value of this colour change remains a mystery. Here we provide an interdisciplinary summary of the current body of knowledge on autumn colours, and discuss unresolved issues and future avenues of research that might help reveal the evolutionary meaning of this spectacle of nature.
TL;DR: In this paper, the catalytic performance of supported ruthenium catalysts for the selective methanation of CO in the presence of excess CO 2 has been investigated with respect to the loading (0.5-5.0 ) and mean crystallite size (1.3-13.6 ).
Abstract: The catalytic performance of supported ruthenium catalysts for the selective methanation of CO in the presence of excess CO 2 has been investigated with respect to the loading (0.5–5.0 wt.%) and mean crystallite size (1.3–13.6 nm) of the metallic phase as well as with respect to the nature of the support (Al 2 O 3 , TiO 2 , YSZ, CeO 2 and SiO 2 ). Experiments were conducted in the temperature range of 170–470 °C using a feed composition consisting of 1%CO, 50% H 2 15% CO 2 and 0–30% H 2 O (balance He). It has been found that, for all catalysts investigated, conversion of CO 2 is completely suppressed until conversion of CO reaches its maximum value. Selectivity toward methane, which is typically higher than 70%, increases with increasing temperature and becomes 100% when the CO 2 methanation reaction is initiated. Increasing metal loading results in a significant shift of the CO conversion curve toward lower temperatures, where the undesired reverse water–gas shift reaction becomes less significant. Results of kinetic measurements show that CO/CO 2 hydrogenation reactions over Ru catalysts are structure sensitive, i.e., the reaction rate per surface metal atom (turnover frequency, TOF) depends on metal crystallite size. In particular, for Ru/TiO 2 catalysts, TOFs of both CO (at 215 °C) and CO 2 (at 330 °C) increase by a factor of 40 and 25, respectively, with increasing mean crystallite size of Ru from 2.1 to 4.5 nm, which is accompanied by an increase of selectivity to methane. Qualitatively similar results were obtained from Ru catalysts supported on Al 2 O 3 . Experiments conducted with the use of Ru catalyst of the same metal loading (5 wt.%) and comparable crystallite size show that the nature of the metal oxide support affects significantly catalytic performance. In particular, the turnover frequency of CO is 1–2 orders of magnitude higher when Ru is supported on TiO 2 , compared to YSZ or SiO 2 , whereas CeO 2 - and Al 2 O 3 -supported catalysts exhibit intermediate performance. Optimal results were obtained over the 5%Ru/TiO 2 catalyst, which is able to completely and selectively convert CO at temperatures around 230 °C. Addition of water vapor in the feed does not affect CO hydrogenation but shifts the CO 2 conversion curve toward higher temperatures, thereby further improving the performance of this catalyst for the title reaction. In addition, long-term stability tests conducted under realistic reaction conditions show that the 5%Ru/TiO 2 catalyst is very stable and, therefore, is a promising candidate for use in the selective methanation of CO for fuel cell applications.
TL;DR: The chemical oxygen demand (COD) elimination reached 95.3% demonstrating that cheese whey could be efficiently used for hydrogen and methane production, in a two-stage process.
Technical University of Denmark1, Simon Fraser University2, University of Southern California3, National Renewable Energy Laboratory4, University of Denver5, University of Texas at Dallas6, University of North Texas7, University of Florida8, University of Pittsburgh9, Eindhoven University of Technology10, Linköping University11, Katholieke Universiteit Leuven12, IMEC13, École Polytechnique Fédérale de Lausanne14, University of Patras15, Ben-Gurion University of the Negev16, Alcan17
TL;DR: A round robin for the performance of roll-to-roll coated flexible large-area polymer solarcell modules involving 18 different laboratories in Northern America, Europe and Middle East is presented in this paper.
TL;DR: In this review, recent advances in understanding the role(s) of receptors and intracellular signalling molecules involved in immune responses are summarized.
TL;DR: In this paper, the effects of platinum loading, photocatalyst content in suspension, glycerol concentration, solution pH and temperature on the reaction rate have been studied in detail.
TL;DR: Kallikrein-related peptidases constitute a single family of 15 (chymo)trypsin-like proteases (KLK1–15) with pleiotropic physiological roles and represent attractive biomarkers for clinical applications and potential therapeutic targets for common human pathologies.
TL;DR: This review combines an account of attempts to achieve a biotechnological valorization of raw glycerol with a review of appropriate literature.
Abstract: Continuous energy crises and increasing demand for conventional fuels has resulted in the need for biofuels on a commercial scale. Transesterification of oils to yield biodiesel – one of the principal biofuels currently produced in large-scale operations – is coupled with significant production of a glycerol-rich water (so-called “crude” or “raw” glycerol), as an important side-product of the process. The increasing demand for biodiesel leads to abundant quantities of this glycerol-rich material on the market. Therefore, glycerol valorization has much to offer in the cost reduction of biodiesel production. To this end, various chemical or biotechnological strategies have been developed to obtain added-value products using crude glycerol as substrate. This review combines an account of our attempts to achieve a biotechnological valorization of raw glycerol with a review of appropriate literature.
TL;DR: It is shown that under certain conditions, the robustness properties of the continuous-time design are inherited by the sampled-data design, as long as the sampling period is not too large.
Abstract: In this work, a sampled-data nonlinear observer is designed using a continuous-time design coupled with an inter-sample output predictor. The proposed sampled-data observer is a hybrid system. It is shown that under certain conditions, the robustness properties of the continuous-time design are inherited by the sampled-data design, as long as the sampling period is not too large. The approach is applied to linear systems and to triangular globally Lipschitz systems.
TL;DR: In this paper, the fracture energy of hybrid carbon fiber reinforced polymers was investigated and the composites were modified by the addition of multi-walled carbon nanotubes into the matrix material.
Abstract: In the present study, the fracture energy of hybrid carbon fiber reinforced polymers was investigated. The composites were modified by the addition of multi-walled carbon nanotubes into the matrix material. The interlaminar fracture properties under Mode I and Mode II remote loading were studied as a function of the carbon nanotube content in the matrix. With the addition of carbon nanotubes in the epoxy matrix, a significant increase in the load bearing ability as well as in the fracture energy was observed, for both Mode I and Mode II tests. It is speculated that carbon nanotubes due to their large aspect ratio have a significant toughening effect since extra energy is needed in order to pull them out from the matrix and start the crack propagation following a kinking out pattern at nanoscale.
TL;DR: In patients treated after the introduction of novel agents, the international staging system (ISS) could discriminate three groups with significantly different outcomes (5-year survival for ISS stage I, II and III was 66, 45 and 18%, respectively, P<0.001).
Abstract: When the novel agents thalidomide, bortezomib and lenalidomide are administered to patients with myeloma in the context of clinical trials, they are associated with a significant improvement in response, progression-free survival and in some studies, overall survival (OS); however, their effect on the outcome of unselected myeloma patients has not been fully assessed. We compared the outcome of 1376 unselected patients with symptomatic myeloma, who started treatment before or after the introduction of thalidomide. The median OS in patients who started treatment after the introduction of novel agents increased by 12 months (48 vs 36 months, P 70 years (from 26 to 33 months, P=0.27). In patients treated after the introduction of novel agents, the international staging system (ISS) could discriminate three groups with significantly different outcomes (5-year survival for ISS stage I, II and III was 66, 45 and 18%, respectively, P<0.001). ISS was also valid in patients who actually received upfront treatment with novel drugs (4-year survival rate was 85, 61 and 26% for ISS stage I, II and III patients, P=0.001).