bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of capillary electrophoresis coupling with electrochemiluminescence detection to estimate activity of leucine aminopeptidas
Authors: Su Ming , Wei Min , Zhou Zhixin , Liu Songqin 
Published: March 2013

ABSTRACTA new method to estimate the leucine aminopeptidase (LAP, EC 3.4.11.1) activity using capillary electrophoresis coupled with electrochemiluminescence (ECL) is described. The liberated proline produced by LAP catalyzing the hydrolysis reaction of leucin–proline was used as an ECL coreagent to enhance Ru(bpy)32+ECL signals efficiently. The detection limit for proline was 2.88 × 10−6 m(signal‐to‐noise ratio 3), which was equal to 9.60 × 10−8units of LAP being used to catalyze leucin–proline for 1 min. The Michaelis constantKm(2.07 × 10−2 mol/L) and the maximum reaction velocityVmax(1.06 × 10−5 mol/L/min) of LAP for leucin–proline are reported. The reaction conditions including the concentration of metal ions, incubation temperature and pH were optimized. This method was successfully applied to detect LAP activity in plasma and the results were in good agreement with that obtained by the clinical method. Copyright © 2013 John Wiley & Sons, Ltd.
A Computational Evaluation of the Evidence for the Synthesis of 1,3‐Dimethylcyclobutadiene in the Solid State and Aqueous Solution
Authors: Rzepa Henry S. 
Published: March 2013

AbstractDensity functional calculations of 1H NMR spectra and reaction barriers at the ωB97XD/6‐311G(d,p)/continuum water level do not support the claimed identification of encarcerated 1,3‐dimethylcyclobutadiene in either the solid state or aqueous solution, as reported by Barboiu et al (Chem. Eur. 2011, 17, 10021). Instead, previous suggestions that the species identified in the solid state is in fact 2‐oxabicyclo[2.2.0]hex‐5‐en‐3‐one (the Dewar lactone Me22) are reaffirmed. Analysis of the ground‐state electronic structure of this species indicates an unusual π‐anomeric effect is promoting a Dunitz‐like chemical reaction pathway leading to the eventual elimination of carbon dioxide and formation of 1,3‐dimethylcyclobutadiene.
Synthesis, Structure, and Electronic Properties of Extended π‐Conjugated Group 6 Fischer Alkoxy–Bis(carbene) Complexes
Authors: Chu Gong M. , Fernández Israel , Sierra Miguel A. 
Published: March 2013

AbstractThe synthesis, structure and electronic properties of novel Group 6 Fischer alkoxy–bis(carbene) complexes are reported. The UV/Vis spectra of these species display two main absorptions at approximately 350 and 550 nm attributable to a ligand‐field (LF) and metal‐to‐ligand charge‐transfer (MLCT) transitions, respectively. The planarity of the system and the cooperative effect of both pentacarbonyl metal moieties greatly enhance the conjugation between the group at the end of the spacer and the metal carbene fragment provoking dramatic changes in the LF and MLCT absorptions. This is in contrast to related push–pull Fischer monocarbenes, where the position of the MLCT band remains mostly unaltered regardless the substituent attached to the donor fragment. In addition, the MLCT maxima can be tuned with subtle modifications of the electronic nature of the central aryl fragment in the novel A–π‐D–π‐A (A=acceptor, D=donor) systems. DFT and time‐dependent (TD) DFT quantum chemical calculations at the B3LYP/def2‐SVP level have also been performed to determine the minimum‐energy molecular structure of this family of compounds and to analyse the nature of the vertical one‐electron excitations associated to the observed UV/Vis absorptions as well as to rationalise their electrochemical behaviour. The ability of tuning up the electronic properties of the compounds studied herein may be of future use in material chemistry.
Macro‐ and Microkinetic Simulation of Diesel Oxidation Catalyst: Effect of Aging, Noble Metal Loading and Platinum Oxidation
Authors: Hauff Karin , Boll Willi , Tischer Steffen , Chan Denise , Tuttlies Ute , Eigenberger Gerhart , Deutschmann Olaf , Nieken Ulrich 
Published: March 2013

AbstractIn automotive exhaust aftertreatment simulation, both macro‐ and microkinetic models are commonly used. In this contribution both models are applied for the simulation of diesel oxidation catalysts (Pt/γ‐Al2O3) with different catalyst loading and degree of thermal aging. The study proves that the structure insensitive kinetics of the considered catalysts can be described with the same rate equations only by scaling the rate constants of the different reaction steps with the catalytically active Pt surface, which is accessible by CO adsorption or light‐off measurements. In addition, NO oxidation is strongly influenced by a reversible, slow transformation of Pt into Pt‐oxide.
Influence of Body Mass Index on Recurrence and Quality of Life in Atrial Fibrillation Patients After Catheter Ablation: A Meta‐Analysis and Systematic Review
Authors: Zhuang Jianhui , Lu Yuyan , Tang Kai , Peng Wenhui , Xu Yawei 
Published: March 2013

AbstractBackgroundAccumulating evidence has demonstrated that overweight and obesity, expressed as high body mass index (BMI), are associated with the development of atrial fibrillation (AF) and quality of life (QoL) in AF patients. However, the role of high BMI as a risk factor for prognosis and QoL in AF patients undergoing ablation remains controversial.HypothesisWe hypothesized that elevated BMI was correlated with AF recurrence and QoL after an ablative procedure.MethodsWe performed a comprehensive search of PubMed, EMBASE, and the Cochrane Library. Studies were included if they investigated the association of BMI with AF recurrence and QoL after ablation.ResultsOf the 151 articles identified, 12 studies that enrolled 3286 individuals met the inclusion criteria. Overall, compared with normal‐BMI patients, AF recurrence occured more frequently in high‐BMI patients after ablation (odds ratio: 1.32, 95% confidence interval: 1.17‐1.5, P < 0.001). However, the pooled esimate of odds ratio adjusted for multiple confounders did not reach significance. The summary weighted mean difference of BMI between patients with and without recurrence was 0.43 (95% confidence interval: 0.05‐0.81, P = 0.027). In addition, QoL scores were significantly lower in high‐BMI than in normal‐BMI patients before the ablative procedure, whereas the gap of QoL between normal‐BMI and high‐BMI groups was decreased at follow‐up.ConclusionsResults of this meta‐analysis suggest 2 points, namely that the tight association between overweight/obesity and AF recurrence after ablation may be partly due to other concomitant conditions, and that impaired QoL in high‐BMI groups is significantly improved after ablation.
Quantitation of the Mitral Tetrahedron in Patients With Ischemic Heart Disease Using Real‐Time Three‐Dimensional Echocardiography to Evaluate the Geometric Determinants of Ischemic Mitral Regurgitation
Authors: Hsuan Chin‐Feng , Yu Hsi‐Yu , Tseng Wei‐Kung , Lin Lung‐Chun , Hsu Kwan‐Lih , Wu Chau‐Chung 
Published: March 2013

AbstractBackgroundIschemic mitral regurgitation (IMR) is common in ischemic heart disease and results in poor prognosis. However, the exact mechanism of IMR has not been fully elucidated.HypothesisQuantitation of the mitral tetrahedron using three‐dimentianl (3D) echocardiography is capable of evaluating the geometric determinants and mechanisms of IMR.MethodsForty patients with a history of ST‐elevation myocardial infarction at least 6 months earlier were studied. Parameters of mitral deformation and global left ventricular (LV) function and shape were evaluated by 2‐dimensional echocardiography. The effective regurgitant orifice (ERO) of IMR was obtained by the quantitative continuous‐wave Doppler technique. Three‐dimensional (3D) echocardiography was applied to assess the mitral tetrahedron.ResultsMitral valvular tenting area (P < 0.001), mitral annular area (P = 0.032), dilation of the LV in diastole, impairment of the LV ejection fraction, and volume of the spherically shaped LV in systole were greater in patients with an ERO ≥20 mm2 than in those with an ERO <20 mm2. In the mitral tetrahedron, only the interpapillary muscle roots distance showed a significant difference (P = 0.004). Multivariate analysis with the logistic regression model showed the systolic mitral tenting area (odds ratio [OR]: 280.49, 95% confidence interval [CI]: 4.59‐1.72 × 104, P = 0.007) and interpapillary muscle distance (OR: 1.50, 95% CI: 1.03‐2.19, P = 0.036) to be independent factors in predicting significant IMR (ERO ≥20 mm2).Conclusions3D echocardiography can be effectively applied in measuring the mitral tetrahedron and evaluating the mechanism of IMR. Mitral valvular tenting and interpapillary muscle distance are 2 independent factors of significant IMR.
Estrogen receptor‐positive/human epidermal growth factor receptor 2‐negative breast tumors
Authors: Groheux David , Hatt Mathieu , Hindié Elif , Giacchetti Sylvie , de Cremoux Patricia , Lehmann‐Che Jacqueline , Martineau Antoine , Marty Michel , Cuvier Caroline , Cheze‐Le Rest Catherine , de Roquancourt Anne , Visvikis Dimitris , Espié Marc 
Published: March 2013

BACKGROUNDThe objective of this prospective study was to evaluate the ability of 18F‐fluorodeoxyglucose (18F‐FDG) positron emission tomography/computed tomography (PET/CT) to predict chemosensitivity in patients with estrogen receptor (ER)‐positive/human epidermal growth factor receptor 2 (HER2)‐negative breast cancer.METHODSSixty‐four consecutive patients underwent 18F‐FDG PET/CT scanning at baseline and after the second course of neoadjuvant chemotherapy (NAC). The evolution (Δ) between the 2 scans of image parameters (maximum standardized uptake value [SUVmax], SUVmean, metabolic tumor volume, and total lesion glycolysis [TLG]) was measured. Correlations between early changes in PET‐derived parameters and pathologic response observed in surgical specimens after the completion of 8 courses of NAC were estimated with Mann‐Whitney U tests. Response prediction on the basis of clinical data, histologic type, or molecular markers also was assessed (Fisher exact test). Receiver operating characteristic (ROC) analysis was used to compare the area under the curve (AUC) of each parameter.RESULTSThe best prediction of chemosensitivity was obtained with ΔTLG (−49% ± 31% in nonresponders vs −73% ± 25% in responders; P < .0001). Among the biologic parameters, only negative progesterone receptor status (57% responders vs 31% nonresponders; P = .04) and luminal B subtype (63% responders vs 22% nonresponders; P = .02) were predictive of a pathologic response. ROC analysis resulted in an AUC of 0.81, 0.73, 0.71, and 0.63 for ΔTLG, ΔSUVmax, luminal subtype, and progesterone receptor status, respectively.CONCLUSIONSWhen patients responded to NAC, the majority of ER‐positive/HER2 negative tumors exhibited partial tumor shrinkage; and the PET parameters that combined volume and activity measurements, such as TLG, offered better accuracy for early prediction than the SUVmax. Negative progesterone receptor status and luminal B subtype had weaker predictive power than PET‐derived parameters. Cancer 2013;119:1960–1968. © 2013 American Cancer Society.
Electrochemical Oxygen Reduction Behavior of Selectively Deposited Platinum Atoms on Gold Nanoparticles
Authors: Sarkar A. , Kerr J. B. , Cairns E. J. 
Published: March 2013

AbstractCarbon‐supported Pt@Au “core‐shell” nanoparticles with varying surface concentration of platinum atoms have been synthesized using a novel redox‐mediated synthesis approach. The synthesis technique allows for a selective deposition of platinum atoms on the surface of prefabricated gold nanoparticles. Energy dispersive spectroscopic analyses in a scanning electron microscope reveal that the platinum to gold atomic ratios are close to the nominal values, validating the synthesis scheme. X‐ray diffraction data indicate an un‐alloyed structure. The platinum to gold surface atomic ratio determined from cyclic voltammetry and copper under‐potential deposition experiments reveal good agreement with the calculated values at low platinum concentration. However, there is an increase in non‐uniformity in the deposition process upon increasing the platinum concentration. Koutecky–Levich analysis of the samples indicates a transition of the total number of electrons transferred (n) in the electrochemical oxygen reduction reaction from two to four electrons upon increasing the surface concentration of platinum atoms. Furthermore, the data indicate that isolated platinum atoms can reduce molecular oxygen but via a two‐electron route. Moreover, successful four‐electron reduction of molecular oxygen requires clusters of platinum atoms.
Two‐Pulse Control of Large‐Amplitude Vibrations in H2+
Authors: Chang Bo Y. , Shin Seokmin , Palacios Alicia , Martín Fernando , Sola Ignacio R. 
Published: March 2013

AbstractA laser‐adiabatic manipulation of the bond (LAMB) scheme using moderately intense fields is proposed to induce and control large‐amplitude oscillations in nuclear wave packets. The present scheme involves an ultrashort UV pump pulse to initially create a wave packet in an excited electronic state of the hydrogen molecular ion and a low‐frequency control pulse, which is switched on after a given time, leading to controllable vibrational trapping. The choice of H2+ as the target exploits the larger dipole values that molecular ions present as the internuclear distance increases. The amplitude and oscillation period of the wave packet is tuned by the field parameters of the control pulse, and more importantly, significant dissociation and ionization losses are prevented by keeping the laser intensities below hundreds of Terawatts. Our numerical simulations, based on the solution of the time‐dependent Schrödinger equation, show that this control of the bond length is achieved in a wide range of moderate intensities and for relatively long pulse durations, from tens to hundreds of femtoseconds.
A Pedagogical Perspective on Ambipolar FETs
Authors: Kang Moon Sung , Frisbie C. Daniel 
Published: March 2013

AbstractThe operation of an ambipolar field‐effect transistor (FET) is described using a simple diagram depicting the gate voltage and channel potential profile relative to the injection threshold voltage of charge carriers. From this diagram, the transition between transistor‐operation regimes and the resulting current–voltage relations can be easily understood. Also, a practical guidance for the operation of an ambipolar FET is provided. In particular, conditions to achieve the true ambipolar regime, which is of particular interest for light‐emitting transistor operation, and a correct method to extract electron and hole mobilities from a given current–voltage curve are presented.
TripleFRET measurements in flow cytometry
Authors: Fábián Ákos , Horváth Gábor , Vámosi György , Vereb György , Szöllősi János 
Published: March 2013

AbstractA frequently used method for viewing protein interactions and conformation, Förster (fluorescence) resonance energy transfer (FRET), has traditionally been restricted to two fluorophores. Lately, several methods have been introduced to expand FRET methods to three species. We present a method that allows the determination of FRET efficiency in three‐dye systems on a flow cytometer. TripleFRET accurately reproduces energy transfer efficiency values measured in two‐dye systems, and it can indicate the presence of trimeric complexes, which is not possible with conventional FRET methods. We also discuss the interpretation of energy transfer values obtained with tripleFRET in relation to spatial distribution of labeled molecules, specifically addressing the limitations of using total energy transfer to determine molecular distance. © 2013 International Society for Advancement of Cytometry
Response to multi‐generational selection under elevated [CO2] in two temperature regimes suggests enhanced carbon assimilation and increased reproductive output in Brassica napus L.
Authors: Frenck Georg , van der Linden Leon , Mikkelsen Teis Nørgaard , Brix Hans , Jørgensen Rikke Bagger 
Published: March 2013

AbstractFunctional plant traits are likely to adapt under the sustained pressure imposed by environmental changes through natural selection. Employing Brassica napus as a model, a multi‐generational study was performed to investigate the potential trajectories of selection at elevated [CO2] in two different temperature regimes. To reveal phenotypic divergence at the manipulated [CO2] and temperature conditions, a full‐factorial natural selection regime was established in a phytotron environment over the range of four generations. It is demonstrated that a directional response to selection at elevated [CO2] led to higher quantities of reproductive output over the range of investigated generations independent of the applied temperature regime. The increase in seed yield caused an increase in aboveground biomass. This suggests quantitative changes in the functions of carbon sequestration of plants subjected to increased levels of CO2 over the generational range investigated. The results of this study suggest that phenotypic divergence of plants selected under elevated atmospheric CO2 concentration may drive the future functions of plant productivity to be different from projections that do not incorporate selection responses of plants. This study accentuates the importance of phenotypic responses across multiple generations in relation to our understanding of biogeochemical dynamics of future ecosystems. Furthermore, the positive selection response of reproductive output under increased [CO2] may ameliorate depressions in plant reproductive fitness caused by higher temperatures in situations where both factors co‐occur.
Wettability Control on ZnO Nanowires Driven by Seed Layer Properties
Authors: Laurenti Marco , Cauda Valentina , Gazia Rossana , Fontana Marco , Rivera Vivian Farías , Bianco Stefano , Canavese Giancarlo 
Published: March 2013

AbstractThis study proposes a way to control the wettability of zinc oxide nanowires (NWs) by properly selecting the kind of seed layer used to promote the growth of the wires. ZnO seed layers were synthesized on silicon and conductive substrates by a physical vapor deposition approach and a wet‐chemical route, namely, the radio frequency magnetron sputtering and the spin‐coating techniques, respectively. ZnO NWs were grown by a hydrothermal method on each kind of seed layer and the results were compared. The morphologies and crystallographic orientations of the seed layers and the resulting NWs were investigated with the aim of correlating the characteristics of the underlying seed layer to those of the resulting NWs. Additional insights were obtained by performing optical contact angle (OCA) measurements on ZnO seed layers to study their wettability behavior immediately after the synthesis processes and two weeks later. Hydrophilic behavior was observed in both sputtered and spin‐coated fresh seed layers. After two weeks of aging, a change in the wettability and a net transition from hydrophilic to hydrophobic behavior was observed in sputtered seed layers, whereas in the spin‐coated films this transition was not so pronounced and was found to be dependent on the precursor concentration. OCA measurements carried out on ZnO NWs showed that the wettability of the NWs is strictly related to the nature of the underlying seed layers and does not depend on the aging time, in contrast to the behavior of the seed layers. Depending on the deposition method, we therefore obtained either highly hydrophilic or superhydrophobic nanowires, which demonstrates the possibility to strongly control the final wetting behavior of these nanostructures for the desired application, such as self‐cleaning surfaces, antireflection coatings, or substrates to anchor biofunctional agents.
Enzymatic production of modified 2‐dodecyl‐sophorosides (biosurfactants) and their characterization
Authors: Recke Verena Kerstin , Gerlitzki Melanie , Hausmann Rudolf , Syldatk Christoph , Wray Victor , Tokuda Harukuni , Suzuki Nobutaka , Lang Siegmund 
Published: March 2013

AbstractAlkyl sophorosides, a special type of sophorolipids, can be produced using Candida bombicola cultures with glucose as main carbon source and 2‐dodecanol as co‐substrate. The dominating component, 2‐dodecyl‐sophoroside SL‐E2‐12, was purified via medium pressure liquid chromatography (MPLC) and used as substrate for further enzymatic modifications. Using β‐glucuronidase in aqueous media the first modification gave a glycosidic cleavage of the acetyl glucose unit leading to 2‐dodecyl‐glucoside GL‐A2‐12. In a subsequent lipase‐catalyzed acylation with sebacic acid in toluene this compound was functionalized regioselectively at the primary C‐6′ position of glucose. Similar lipase‐catalyzed reactions in toluene, but now using SL‐E2‐12 as acyl acceptor and unusual hydroxyl fatty acids – 3‐hydroxy decanoic acid and 17‐hydroxy stearic acid – as acyl donors, resulted in mono‐ and diacylations of primary hydroxyl positions of the sophorose unit (C‐6′ and C‐6′′) as shown by NMR and MS studies. In physicochemical characterization experiments the new glycoconjugates lowered the surface tension of water from 72 to 27–32 mN/m. Moreover it was observed that the new products inhibit the growth of particular Gram‐positive bacteria. Additionally they indicate potential for anti‐tumor promoting activity.Practical applications: According to literature data 2‐alkyl‐sophorosides can be produced using Candida bombicola cultures with yields of more than 20 g/L. Based on this starting material, 2‐dodecyl‐sophoroside, several regioselective enzymatic modifications were performed. Initially, β‐glucuronidase catalysis in aqueous buffer solution gave 2‐dodecyl‐glucoside which was then successfully acylated at the C‐6 position of glucose by lipase catalysis using a common dicarboxylic acid, sebacic acid. The resulting free carboxylic function of the acidic derivative opens up the possibility of achieving additional chemo‐enzymatic reactions at this position for conversion, for instance, into polyesters. In addition lipase catalysis in organic solvents of 2‐dodecyl‐sophoroside allows acylation with unusual hydroxyl fatty acids of microbial origin. Physicochemical studies showed that these new glycoconjugates may be of interest for the cosmetic industry due to moisture conservation of the skin. For practical applications the conditions of the above biocatalytic reactions have been improved and scaled up.
Tropos, Nevertheless Conformationally Stable Biphenyl Derivatives
Authors: Haberhauer Gebhard , Tepper Christina , Wölper Christoph , Bläser Dieter 
Published: March 2013

AbstractBiphenyl derivatives with small substituents in the ortho and ortho′ positions are called tropos. Due to the low rotation barrier around the C–C bond connecting the two phenyl units, the isolation of only one conformer is not possible; thus they are conformationally unstable. Using DFT calculations, we were able to show that using a suitable peptidic bridging unit, biphenyl systems can become conformationally stable. This stabilization should be independent of the type of substituent in the ortho and ortho′ positions. Some of the proposed biphenyl derivatives were successfully synthesized and studied in solution and solid state. The recorded VT‐NMR, 2D‐NMR and CD spectra show that all biphenyl derivatives exhibit the P conformation. The preference for the P conformation is confirmed by the structure of a biphenyl derivative in solid state.