bluuebunny/crossref_metadata_2025_split huggingface dataset:
Moderate correlation between breath‐holding and CO2 inhalation/hyperventilation methods for transcranial doppler evaluation of cerebral vasoreactivity
Authors: Haussen Diogo C. , Katsnelson Michael , Rodriguez Abiezer , Campo Nelly , Campo‐Bustillo Iszet , Romano Jose G , Koch Sebastian 
Published: May 2012

AbstractBackground.Both CO2 inhalation followed by hyperventilation and breath‐holding have been utilized to measure cerebral vasomotor reactivity (VMR) but their correlation has been poorly studied and understood.Methods.A retrospective study was conducted in 143 subjects (62.6 ± 15.8 years old, 64% men) with transcranial Doppler ultrasonography measurement of mean flow velocity (MFV) at baseline, after 30 seconds of breath‐holding, and after CO2 inhalation followed by hyperventilation, in the left and right middle cerebral artery. Breath‐holding index (BHI) was calculated as the percentage of MFV increase from baseline per second of apnea. CO2 inhalation/hyperventilation index (CO2/HV) was calculated as the percentage of MFV difference between CO2 inhalation and hyperventilation.Results.There were 75 carotid arteries with >70% stenosis or occlusion, and 18 middle cerebral arteries with >50% stenosis or occlusion. The mean BHI was 0.93 ± 0.7 and 0.89 ± 0.6, whereas the mean CO2/HV was 61 ± 26% and 60 ± 26%, respectively, on the right and left sides. The correlation between BHI and CO2/HV was moderate on the right (r = 0.33; p < 0.01) and left sides (r = 0.38; p < 0.01). Multivariate linear regression analysis indicated that age (p = 0.01) and history of stroke (p = 0.007) were associated independently with an impaired VMR on the right as measured by CO2/HV. No predictors for impaired VMR by CO2/HV on the left and by BHI on either side were found.Conclusions.CO2/HV and BHI are only moderately correlated. Further studies are necessary to determine which method more accurately predicts clinical morbidity. © 2012 Wiley Periodicals, Inc. J Clin Ultrasound 2012; Published online in Wiley Online Library
Adaptation to potassium starvation of wild‐type and K+‐transport mutant (trk1,2) of Saccharomyces cerevisiae: 2‐dimensional gel electrophoresis‐based proteomic approach
Authors: Gelis Samuel , Curto Miguel , Valledor Luis , González Asier , Ariño Joaquín , Jorrín Jesús , Ramos José 
Published: May 2012

AbstractSaccharomyces cerevisiae wild‐type (BY4741) and the corresponding mutant lacking the plasma membrane main potassium uptake systems (trk1,trk2) were used to analyze the consequences of K+ starvation following a proteomic approach. In order to trigger high‐affinity mode of potassium transport, cells were transferred to potassium‐free medium. Protein profile was followed by two‐dimensional (2‐D) gels in samples taken at 0, 30, 60, 120, 180, and 300 min during starvation. We observed a general decrease of protein content during starvation that was especially drastic in the mutant strain as it was the case of an important number of proteins involved in glycolysis. On the contrary, we identified proteins related to stress response and alternative energetic metabolism that remained clearly present. Neural network‐based analysis indicated that wild type was able to adapt much faster than the mutant to the stress process. We conclude that complete potassium starvation is a stressful process for yeast cells, especially for potassium transport mutants, and we propose that less stressing conditions should be used in order to study potassium homeostasis in yeast.
Charge carrier mobility, photovoltaic, and electroluminescent properties of anthracene‐based conjugated polymers bearing randomly distributed side chains
Authors: Usluer Özlem , Kästner Christian , Abbas Mamatimin , Ulbricht Christoph , Cimrova Vera , Wild Andreas , Birckner Eckhard , Tekin Nalan , Sariciftci Niyazi Serdar , Hoppe Harald , Rathgeber Silke , Egbe Daniel A. M. 
Published: May 2012

AbstractThis article reports on the synthesis, characterization, and properties of various anthracene‐containing poly (p‐phenylene‐ethynylene)‐alt‐poly(p‐phenylene‐vinylene) (PPE‐PPV) polymers (AnE‐PVs) bearing statistical distributions of various side chains. Primarily, the ratio of linear octyloxy and branched 2‐ethylhexyloxy side chains at the poly(p‐phenylene vinylene) (PPV) parts was varied, leading to the polymers stat, stat1, and stat2. Furthermore, polymers also containing asymmetric substituted PPV and poly(p‐phenylene ethynylene) units (bearing methoxy and 2‐ethylhexyloxy side chains) were prepared yielding stat3, stat4, and stat5. These materials exhibit a broad variation in their photovoltaic properties. It is once more shown that side chains and their distribution can crucially affect the photovoltaic device performance. The introduction of units with asymmetric substitution into these systems seems to be harmful for their utilization in photovoltaic applications. Organic field‐effect transistors were fabricated to investigate hole mobilities in these new materials. Large variance was observed, falling in the range of almost two orders of magnitude, indicating rather different π–π stacking behavior of the polymer backbones owing to side‐chain modifications. Moreover, a selection of the new polymeric systems was investigated regarding their potential for light‐emitting diode (LED) applications. Polymer LEDs using the polymers AnE‐PVstat, ‐stat3, ‐stat4, and ‐stat5, as the active layer showed turn‐on voltage of ∼2 V and exhibited red light emission. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Thermally induced fixed diradical generation on solid supports for surface‐initiated polymerization
Authors: Gure Baris , Bicak Niyazi 
Published: May 2012

AbstractA method is presented for generation of all surface‐bound radicals on solid polymer surfaces. Thus, secondary amide group of newly synthesized crosslinking comonomer, methacryloyloxyethyl methacrylamide was determined as versatile precursor for generation fixed diradicals on solid microspheres, obtained by copolymerization with methyl methacrylate (MMA) in aqueous suspension. Nitrosoation of the secondary amide groups on the microbeads and followed thermolysis above 90 °C was demonstrated to give surface‐bound radicals, capable of initiating polymerization of vinyl monomers, such as; styrene, MMA, N‐vinyl formamide, and N‐vinyl, 2‐pyrrolidone, as evidenced by H NMR, Fourier transform infrared, thermogravimetric analysis, and differential scanning calorimeter techniques. Appreciable grafting yields (55.1%–286.1%) and low free‐homopolymer formation (7.2%–19.7%) were noted within 6 h of the grafting at 100 °C in each case. This strategy involving the use of amide functional crosslinker seemed to be generally applicable to generate surface‐bound radicals for surface‐initiated polymerization from various solid substrates. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Porphyrin derivatives act as vinylene monomers in TEMPO‐mediated radical copolymerization with styrene
Authors: Obata Makoto , Ohtake Eiko , Hirohara Shiho , Tanihara Masao , Yano Shigenobu 
Published: May 2012

AbstractIn this article, we offer clear evidence for the radical copolymerizability of porphyrin rings in 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO)‐mediated radical copolymerizations with styrene. The radical copolymerizations of styrene with 5,10,15,20‐tetrakis(pentafluorophenyl)porphyrin (H2TFPP) was conducted using 1‐phenyl‐1‐(2,2,6,6‐tetramethyl‐1‐piperidinyloxy)ethane as an initiator. The refractive index (RI) traces for the size‐exclusion chromatography of the resulting copolymers were unimodal with narrow molecular weight distributions. The RI traces shifted toward higher molecular weight regions as the polymerization progressed, and the number‐average molecular weights were close to those calculated on the basis of the feed compositions and monomer conversions. These features were in good agreement with a TEMPO‐mediated mechanism. The traces recorded by the ultraviolet‐visible (UV‐vis) detector (430 nm) were identical to those obtained by the RI detector, indicating a statistical copolymerization of styrene with H2TFPP. This also indicated that H2TFPP acted as a monomer and not as a terminator or a chain‐transfer agent under the conditions used. A benzyl radical addition to H2TFPP was conducted as a model reaction for the copolymerization using tributyltin hydride as a chain‐transfer agent, affording a reduced porphyrin, 2‐benzyl‐5,10,15,20‐tetrakis(pentafluorophenyl)chlorin 1, via radical addition to the β‐pyrrole position. The UV‐vis spectrum of 1 was fairly similar to that of poly(styrene‐co‐H2TFPP), indicating that H2TFPP polymerized at its β‐pyrrole position in the TEMPO‐mediated radical polymerization. TEMPO‐mediated radical copolymerizations of styrene with several porphyrin derivatives were also demonstrated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Influence of the graphite type on the synthesis of polypropylene/graphene nanocomposites
Authors: Milani Marcéo A. , Quijada Raul , Basso Nara R. S. , Graebin Ana P. , Galland Griselda B. 
Published: May 2012

AbstractIn this work, the synthesis of polypropylene (PP)/graphene nanosheet (GNS) nanocomposites by in situ polymerization using metallocene catalysts was studied. Initial reactions were performed using rac‐Et(Ind)2ZrCl2 and rac‐Me2Si(Ind)2ZrCl2 catalysts to select the best one to obtain good molecular weight, thermal properties, and tacticity. Subsequently, PP nanocomposites with different loadings of GNS were obtained. GNS from two different sources [Graphite Nacional (GN) and Graphite Aldrich (GA)] have been used, and the differences between the obtained nanocomposites were evaluated. The GNS and nanocomposites were studied by scanning electronic microcopy, transmission electronic microcopy, and X‐ray diffraction. They showed that the GN nanosheets had lower crystal size and diameter than the GA nanosheets and dispersed better in the PP matrix. Differential scanning calorimetry analyses of both types of nanocomposites showed an increase in the crystallization temperature with increasing graphite loading. The polymeric materials were also characterized by GPC, thermogravimetric analysis, and 13C NMR. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Well‐defined amphiphilic polymethylene‐b‐poly(acrylic acid) diblock copolymers: New synthetic strategy and their self‐assembly
Authors: Lu Hui‐Chao , Xue Yang , Zhao Qiao‐Ling , Huang Jin , Xu Shen‐Gang , Cao Shao‐Kui , Ma Zhi 
Published: May 2012

AbstractWell‐defined amphiphilic polymethylene‐b‐poly (acrylicacid) diblock copolymers have been synthesized via a new strategy combining polyhomologation and atom transfer radical polymerization (ATRP). Hydroxyl‐terminated polymethylenes (PM‐OH) with different molecular weights and narrow molecular weight distribution are obtained through the polyhomologation of dimethylsulfoxonium methylides following quantitative oxidation via trimethylamine‐N‐oxide dihydrate. Subsequently, polymethylene‐based macroinitiators (PM‐MIs Mn = 1,300 g mol−1 [Mw/Mn = 1.11] and Mn = 3,300 g mol−1 [Mw/Mn = 1.04]) are synthesized by transformation of terminal hydroxyl group of PM‐OH to α‐haloester in ∼100% conversion. ATRPs of tert‐butyl acrylate (t‐BuA) are then carried out using PM‐MIs as initiator to construct PM‐b‐P(t‐BuA) diblock copolymers with controllable molecular weight (Mn = 8,800–15,800 g mol−1
Mw/Mn = 1.04–1.09) and different weight ratio of PM/P(t‐BuA) segment (1:1.7–1:11.2). The amphiphilic PM‐b‐PAA diblock copolymers are finally prepared by hydrolysis of PM‐b‐P(t‐BuA) copolymers and their self‐assembly behavior in water is preliminarily investigated via the determination of critical micelle concentrations, dynamic light scattering, and transmission electron microscope (TEM). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Dynamic mechanical properties of polystyrene ionomers containing both carboxylate and sulfonate anionic groups
Authors: Song Ju‐Myung , Ko Kwang‐Hwan , Kim Joon‐Seop , Shin Kwanwoo 
Published: May 2012

AbstractPolystyrene‐based ionomers possessing sodium methacrylate (MA) and sodium styrenesulfonate (SS) units in each polymer chain [poly(styrene‐co‐methacrylate‐co‐styrenesulfonate) (PSMA‐SS)] were synthesized. The dynamic mechanical properties of PSMA‐SS ionomers were studied and compared with those of styrene ionomers containing only MA (PSMA ionomer) or SS (PSS ionomer) units. It was observed that the ionic moduli of PSMA‐SS ionomers depended directly on the total ion content and that the ionic modulus was highest for the PSMA ionomer and lowest for the PSMA‐SS ionomer. The matrix Tgs of the three ionomer systems were found to be similar to each other; the cluster Tg of PSMA‐SS ionomer was higher than that of PSS ionomer at low SS contents but became closer to each other at high SS contents. In addition, the small‐angle X‐ray scattering study revealed that the multiplet size might be in the following order: PSMA‐SS > PSS > PSMA. This implied that at the same ion content, the fractions of cluster regions were smallest for PSMA‐SS ionomer in comparison with those of PSS or PSMA ionomers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Dimeric analogs of immunosuppressive decapeptide fragment of ubiquitin
Authors: Kluczyk Alicja , Cydzik Marzena , Biernat Monika , Bąchor Remigiusz , Pasikowski Paweł , Stefanowicz Piotr , Artym Jolanta , Zimecki Michał , Szewczuk Zbigniew 
Published: May 2012

Our previous studies revealed that ubiquitin and its decapeptide fragment with the LEDGRTLSDY sequence, located on the exposed molecule loop, strongly suppressed the immune response. This suggested that the loop may serve as a functional epitope of ubiquitin molecule and that a possible mechanism of biological action of the synthesized peptides is associated with interfering in interactions of ubiquitin with other molecules. Ubiquitin is known to exist in oligomeric forms, which can interact with various oligomeric receptors. We designed and synthesized new dimeric analogs of the ubiquitin fragment, to probe whether dimeric peptides may have higher affinity towards the ubiquitin receptors responsible for immunosuppression, which are believed to form oligomeric structures. Three dimerization strategies, N‐terminus to N‐terminus, C‐terminus to C‐terminus, and N‐terminus to C‐terminus (head‐to‐tail) via PEG derivatives were used to synthesize the dimeric peptides on solid support. In the course of our research, we developed a new and straightforward procedure of dimerization where α‐amino groups of the C‐terminal lysine residues of two peptide fragments were linked by PEG spacer directly on solid support.The effect of dimeric analogs on the immunological response was tested in the AFC in vitro experiment. The immunological tests showed that the head‐to‐tail dimerization caused a more profound increase in the biological activity than other tested dimerization methods. Our results suggest that such orientation of peptide components may correspond to orientation of the hypothetic ubiquitin receptors responsible for the immunomodulatory activity. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.
Luminescence studies of isolated ZnO nanowires grown by the vapour‐liquid‐solid method
Authors: Martínez Oscar , Güell Frank , Hortelano Vanesa , Jiménez Juan , Cornet Albert , Morante Joan Ramon 
Published: May 2012

AbstractIn this work we analysed, by means of Spectral Imaging Cathodoluminescence, the luminescence properties of individual ZnO nanowires (NWs) grown by chemical vapour deposition. The NWs show a general increase of the radiative recombination channels, and a decrease of the relative intensity of the visible band respect to the bound exciton emission, pointing to a high crystal quality. Local changes in the peak position and intensity of the near band edge were found by studying the luminescence of individual NWs, which have been ascribed to structural changes along them (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High sensitivity hydrogen sensors based on GaN
Authors: Yatskiv Roman , Grym Jan , Zdansky Karel 
Published: May 2012

AbstractHigh quality graphite based Schottky diodes are presented. Schottky barriers were prepared by mechanical deposition of colloidal graphite on GaN substrates uncoverd and partly covered with Pt nanoparticles deposited by electrophoretic techniques. The electron transport for both diodes can be well described by thermionic emission. Hydrogen sensing characteristics of graphite‐Pt/GaN Schottky diodes were investigated. Temperature dependence of the sensitivity, the barrier height variation, the ideality factor and the barrier height itself were studied. The proposed hydrogen sensor responds well to various hydrogen containing gases. The room‐temperature sensitivity response of 2x107 was obtained in 1000 ppm H2/N2ambient. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Emission and elastic strain in InGaAs/GaAs quantum wells with embedded InAs quantum dots
Authors: Vega‐Macotela L. G. , Polupan G. , Shcherbyna Ye. 
Published: May 2012

AbstractPhotoluminescence (PL) spectra have been studied in the symmetric GaAs/In0.15Ga0.85As/GaAs quantum wells (QWs) with embedded InAs quantum dots (QDs), grown at different temperatures from the range 470‐535 °C. The increase of QD growth temperature is accompanied by decreasing the QD surface density and the enlargement of QD lateral diameters. Simultaneously the variation of the PL intensity and PL peak positions none monotonously have been detected. To understand the reason of the variation of PL intensity and peak positions the PL temperature dependences and the X‐ray diffraction (XRD) at low angles (1.75‐1.92°) have been studied. The fitting procedure is applied to analysis the temperature shift of PL peak positions. Fitting has been done on the base of empirical expression for the band gap shrinkage that uses the Einstein temperature parameter. The character non monotonous for the Ga/In inter diffusion versus QD growth temperatures has been revealed. The XRD study has detected the high intensity peaks that corresponds to the diffraction of X‐ray beam from the (311) crystal planes in GaAs QWs. The position of XRD peaks in the structures with QD grown at 490‐510 °C is very close to the angles related to the diffraction from (311) planes in the bulk GaAs. In QD structures with QD grown at 470 and 525‐535 °C the (311) XRD peaks shift to the higher diffraction angles that testifies on the essential compressive strains in these structures. The reason of the variation non monotonously of elastic strain versus QD densities has been discussed (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of InAs/GaSb type‐II superlattice photodiodes for mid‐wave IR with different mesa sidewall passivation schemes
Authors: Karim Amir , Marcks von Würtemberg Rickard , Asplund Carl , Malm Hedda , Andersson Jan , Plis Elena , Krishna Sanjay 
Published: May 2012

AbstractWe report on the electrical and material characterization of InAs/GaSb type‐II superlattice (T2SL) mid‐wave infrared (MWIR) photodiodes with different passivation schemes on the mesa‐sidewalls with significant differences in the resulting low temperature dark currents. Devices fabricated by dry etching and passivated with polymerized photoresist, show orders of magnitude lower dark currents as compared to unpassivated devices. The mesa side walls were examined using high resolution transmission electron microscopy (HRTEM) with a special focus on the interface between the superlattice material and the dielectric passivation. Material analysis on nanometer scale at the mesa sidewall interface was performed using energy dispersive X‐ray (EDX) spectrometry. EDX line scans were obtained from interfaces for different passivated and unpassivated devices, using the highly focused electron beam in TEM, to investigate the chemical compositions. The unpassivated and photoresist‐passivated mesas, with different electrical properties, revealed different sidewall morphologies and compositions. An oxygen containing layer was observed in photoresist‐passivated devices covering the whole mesa sidewall. We think this plays a role in reducing surface leakage dark current. In HR‐TEM the mesa sidewall topography reveals preferential etching of one superlattice component as previously observed. Nevertheless, the dielectric material covers the sidewall uniformly (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Irradiation induced nanotrack and property modification in Zn3P2
Authors: Sudhakar Selvakumar , Nagarajan Mony , Baskar Krishnan 
Published: May 2012

AbstractZn3P2 epilayers were grown on InP (100) substrates by liquid phase epitaxy (LPE) using In solvent. Zinc composition in the epilayers was varied by changing the zinc mole fraction in the growth melt and was confirmed by energy dispersive X‐ray analysis (EDAX). Stoichiometric Zn3P2 epilayers were subjected to 100 MeV Ni ion irradiation with various ion fluences of 1 × 1010 to 1 × 1013 ions/cm2 at 77 K. From the high resolution X‐ray diffraction (HRXRD) of 100 MeV Ni ion irradiated epilayers, the decrease in the peak intensities and increase in the FWHM values were observed. AFM analysis revealed the formation of nanotracks in the irradiated Zn3P2 epilayers. Hall measurements showed the decrease in carrier mobility with the increase of ion fluence. The absorption band edge of Zn3P2 gradually decreased from 1.49 eV to 1.42 eV upon increasing the ion fluence (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lösungen für energieeffiziente multifunktionale Verglasungen
Authors: Schneider Frank 
Published: May 2012

AbstractDie Glasfassade muss heute Aufgaben übernehmen, die längst über die ursprüngliche Anwendung als wärmedämmender Raumabschluss hinausgehen. Insbesondere der sommerliche Überhitzungsschutz spielt eine entscheidende Rolle. Intelligent gestaltete Glasfassaden sind aber durchaus in der Lage den Energieverbrauch eines Gebäudes positiv zu reduzieren und den Nutzungskomfort zu verbessern. Zunächst soll auf die grundlegenden bauphysikalischen Parameter eingegangen werden, die ein Isolierglas charakterisieren. Anschließend werden anhand von Beispielen Lösungen für multifunktionale Gebäudehüllen aus Glas aufgezeigt.