bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gas‐Phase Peptide Structures Unraveled by Far‐IR Spectroscopy: Combining IR‐UV Ion‐Dip Experiments with Born–Oppenheimer Molecular Dynamics Simulations
Authors: Jaeqx Sander , Oomens Jos , Cimas Alvaro , Gaigeot Marie‐Pierre , Rijs Anouk M. 
Published: February 2014

AbstractVibrational spectroscopy provides an important probe of the three‐dimensional structures of peptides. With increasing size, these IR spectra become very complex and to extract structural information, comparison with theoretical spectra is essential. Harmonic DFT calculations have become a common workhorse for predicting vibrational frequencies of small neutral and ionized gaseous peptides.1 Although the far‐IR region (<500 cm−1) may contain a wealth of structural information, as recognized in condensed phase studies,2 DFT often performs poorly in predicting the far‐IR spectra of peptides. Here, Born–Oppenheimer molecular dynamics (BOMD) is applied to predict the far‐IR signatures of two γ‐turn peptides. Combining experiments and simulations, far‐IR spectra can provide structural information on gas‐phase peptides superior to that extracted from mid‐IR and amide A features.
Electrochemistry of Nanoparticles
Authors: Kleijn Steven E. F. , Lai Stanley C. S. , Koper Marc T. M. , Unwin Patrick R. 
Published: February 2014

AbstractMetal nanoparticles (NPs) find widespread application as a result of their unique physical and chemical properties. NPs have generated considerable interest in catalysis and electrocatalysis, where they provide a high surface area to mass ratio and can be tailored to promote particular reaction pathways. The activity of NPs can be analyzed especially well using electrochemistry, which probes interfacial chemistry directly. In this Review, we discuss key issues related to the electrochemistry of NPs. We highlight model studies that demonstrate exceptional control over the NP shape and size, or mass‐transport conditions, which can provide key insights into the behavior of ensembles of NPs. Particular focus is on the challenge of ultimately measuring reactions at individual NPs, and relating the response to their structure, which is leading to imaginative experiments that have an impact on electrochemistry in general as well as broader surface and colloid science.
Unexpected Formation of a [4]Radialene and Dendralenes by Addition of Tetracyanoethylene to a Tetraaryl[5]cumulene
Authors: Januszewski Johanna A. , Hampel Frank , Neiss Christian , Görling Andreas , Tykwinski Rik R. 
Published: February 2014

AbstractThe use of cumulenes in synthetic transformations offers the possibility to form structurally interesting and potentially useful conjugated molecules. The cycloaddition reaction of a tetraaryl[5]cumulene with the electron‐deficient olefin tetracyanoethylene affords unusual products, including functionalized dendralenes and alkylidene cyclobutanes, as well as a symmetric [4]radialene that shows unique solvatochromism, with λmax values approaching the near‐IR region. These carbon‐rich products have been investigated spectroscopically and by X‐ray crystallographic analysis (five structures). The cycloaddition reaction sequence has also been explored by mechanistic and theoretical studies. The obtained results clearly demonstrate the potential of [5]cumulenes to serve as precursors for unprecedented conjugated structures.
Nanosized Heterostructures of Au@Prussian Blue Analogues: Towards Multifunctionality at the Nanoscale
Authors: Maurin‐Pasturel Guillaume , Long Jérôme , Guari Yannick , Godiard Franck , Willinger Marc‐Georg , Guerin Christian , Larionova Joulia 
Published: February 2014

AbstractAccess to multifunctionality at the nanoscale requires the development of hybrid nanostructures that combine materials of different natures. In this line of thought, current research on coordination polymers is not only focusing on their synthesis at the nanoscale, but also on combining these polymers with other materials. According to a novel and rational approach, single‐layer Au@Prussian blue analogue (PBA) and double‐layer Au@PBA@PBA′ core–shell nanoparticles (NPs) may be obtained through the growth of a cyano‐bridged coordination network on the gold surface. The nanosized heterostructures combine the plasmonic optical properties of the gold core and the magnetic properties of the PBA shell. Whereas the single‐layer nanoparticles are paramagnetic, the double‐layer nanostructures display ferromagnetism; therefore, the overall structural motif may be considered as multifunctional. The developed synthetic concept also includes an easy access to hollow PBA NPs.
Dismutational and Global‐Minimum Isomers of Heavier 1,4‐Dimetallatetrasilabenzenes of Group 14
Authors: Jana Anukul , Huch Volker , Repisky Michal , Berger Raphael J. F. , Scheschkewitz David 
Published: February 2014

AbstractAromatic species with heavier Group 14 elements show remarkable differences in terms of stability, structure, and reactivity. Herein we report our experimental and theoretical investigations regarding isomers of germanium‐ and tin‐containing benzene analogues E2Si4R6 (E=Ge, Sn). The germanium‐substituted dismutational isomer with a tricyclic six‐membered scaffold is isolable, but unlike the homonuclear Si6 analogue slowly rearranges even at room temperature to give the propellane‐type global minimum isomer. In case of E=Sn the dismutational isomer may be an intermediate on the pathway to the propellane‐type species obtained, but cannot be detected even at low temperature. Unprecedentedly large chemical shift anisotropies in the 29Si NMR spectra that increase from the Si6 species through Ge2Si4 to Sn2Si4 are rationalized by progressively larger paramagnetic‐term contributions to the chemical shift tensor as a result of diminishing HOMO–LUMO gaps, which are also reflected in the absorption spectra, as well as by appearance and symmetry of these frontier orbitals.
Superconducting Double Perovskite Bismuth Oxide Prepared by a Low‐Temperature Hydrothermal Reaction
Authors: Rubel Mirza H. K. , Miura Akira , Takei Takahiro , Kumada Nobuhiro , Mozahar Ali M. , Nagao Masanori , Watauchi Satoshi , Tanaka Isao , Oka Kengo , Azuma Masaki , Magome Eisuke , Moriyoshi Chikako , Kuroiwa Yoshihiro , Azharul Islam A. K. M. 
Published: February 2014

AbstractPerovskite‐type structures (ABO3) have received significant attention because of their crystallographic aspects and physical properties, but there has been no clear evidence of a superconductor with a double‐perovskite‐type structure, whose different elements occupy A and/or B sites in ordered ways. In this report, hydrothermal synthesis at 220 °C produced a new superconductor with an A‐site‐ordered double perovskite structure, (Na0.25K0.45)(Ba1.00)3(Bi1.00)4O12, with a maximum Tc of about 27 K.
New biodiesel additives from glycerol and isoamylenes
Authors: Izquierdo José Felipe , Outón Pablo R. , Galán Maribel , Jutglar Luis , Villarrubia Miguel , Ariza Xavier 
Published: February 2014

AbstractThe etherification of glycerol and isoamylenes was performed using several macromolecularion‐exchange resins in order to find the best catalyst which would provide the maximum conversion of glycerol and higher selectivities to ethers. Some different organic solvents (tert‐amyl alcohol, 1,4‐dioxane, acetonitrile, n‐hexane, dichloromethane, diisopropylamine and dimethylformamide) were used in the etherification of glycerol. Reactions were carried out in a batch autoclave reactor at 1.5 MPa in the temperature range from 25 to 100 °C for 24 h of contact time. It was found that resins with a greater pore volume and greater pore diameter showed a better performance in solventless reactions, but when employing solvents their polarity was responsible for the distinct results obtained in the conversion of glycerol: relative abundance and composition of the polar and non‐polar phases in the final reaction mixture. The solubilization of glycerol and isoamylenes in the reaction mixture seems to be the main factor in the progress of the reaction, which is reflected in the different amount of ethers primarily obtained in the non‐polar phase. tert‐Amyl alcohol showed the best results in terms of conversion of glycerol due to the total miscibility of both reactants but it must be employed at temperatures below 50 °C in order to avoid its dehydration reaction that reduces the catalyst activity.
Reasons for non-participation in population-based abdominal aortic aneurysm screening
Authors: Linne A , Leander K , Lindström D , Törnberg S , Hultgren R 
Published: February 2014

Abstract

Background
A population-based screening programme for abdominal aortic aneurysm (AAA) started in 2010 in Stockholm County, Sweden. This present study used individual data from Sweden's extensive healthcare registries to identify the reasons for non-participation in the AAA screening programme.

Methods
All 65-year-old men in Stockholm are invited to screening for AAA; this study included all men invited from July 2010 to July 2012. Participants and non-participants were compared for socioeconomic factors, travel distance to the examination centre and healthcare use. The influence of these factors on participation was analysed using univariable and multivariable logistic regression models.

Results
The participation rate for AAA screening was 77·6 per cent (18 876 of 24 319 men invited). The prevalence of AAA (aortic diameter more than 2·9 cm) among participants was 1·4 per cent. The most important reasons for non-participation in the multivariable regression analyses were: recent immigration (within 5 years) (odds ratio (OR) 3·25, 95 per cent confidence interval 1·94 to 5·47), low income (OR 2·76, 2·46 to 3·10), marital status single or divorced (OR 2·23, 2·08 to 2·39), low level of education (OR 1·28, 1·16 to 1·40) and long travel distance (OR 1·23, 1·10 to 1·37). Non-participants had a higher incidence of stroke (4·5 versus 2·8 per cent; P &lt; 0·001) and chronic pulmonary disease (2·9 versus 1·3 per cent; P &lt; 0·001). Daily smoking was more common in residential areas where the participation rate for AAA screening was low.

Conclusion
Efforts to improve participation in AAA screening should target the groups with low income, a low level of education and immigrants. The higher morbidity in the non-participant group, together with a higher rate of smoking, make it probable that this group also has a high risk of AAA.
Outcomes reported in high-impact surgical journals
Authors: Antonescu I , Mueller C L , Fried G M , Vassiliou M C , Mayo N E , Feldman L S 
Published: February 2014

Abstract

Background
With advances in operative technique and perioperative care, traditional endpoints such as morbidity and mortality provide an incomplete description of surgical outcomes. There is increasing emphasis on the need for patient-reported outcomes (PROs) to evaluate fully the effectiveness and quality of surgical interventions. The objective of this study was to identify the outcomes reported in clinical studies published in high-impact surgical journals and the frequency with which PROs are used.

Methods
Electronic versions of material published between 2008 and 2012 in the four highest-impact non-subspecialty surgical journals (Annals of Surgery, British Journal of Surgery (BJS), Journal of the American College of Surgeons (JACS), Journal of the American Medical Association (JAMA) Surgery) were hand-searched. Clinical studies of adult patients undergoing planned abdominal, thoracic or vascular surgery were included. Reported outcomes were classified into five categories using Wilson and Cleary's conceptual model.

Results
A total of 893 articles were assessed, of which 770 were included in the analysis. Some 91·6 per cent of studies reported biological and physiological outcomes, 36·0 per cent symptoms, 13·4 per cent direct indicators of functional status, 10·6 per cent general health perception and 14·8 per cent overall quality of life (QoL). The proportion of studies with at least one PRO was 38·7 per cent overall and 73·4 per cent in BJS (P &lt; 0·001). The proportion of studies using a formal measure of health-related QoL ranged from 8·9 per cent (JAMA Surgery) to 33·8 per cent (BJS).

Conclusion
The predominant reporting of clinical endpoints and the inconsistent use of PROs underscore the need for further research and education to enhance the applicability of these measures in specific surgical settings.
Impact of risk scoring on decision-making in symptomatic moderate carotid atherosclerosis
Authors: Dharmarajah B , Thapar A , Salem J , Lane T R A , Leen E L S , Davies A H 
Published: February 2014

Abstract

Background
Benefit from carotid endarterectomy (CEA) in symptomatic moderate (50–69 per cent) carotid stenosis remains marginal. The Fourth National Clinical Guideline for Stroke recommends use of the risk score from the European Carotid Surgery Trial (ECST) to aid decision-making in symptomatic carotid disease. It is not known whether clinicians are, in fact, influenced by it.

Methods
Using the ECST risk prediction model, three scenarios of patients with a low (less than 10 per cent), moderate (20–25 per cent) and high (40–45 per cent) 5-year risk of stroke were devised and validated. Invitations to complete an online survey were sent by e-mail to vascular surgeons and stroke physicians, with responses gathered. The questionnaire was then repeated with the addition of the ECST risk score.

Results
Two hundred and one completed surveys were analysed (21·5 per cent response rate): 107 by stroke physicians and 94 by vascular surgeons. The high-risk scenario after the introduction of the ECST risk score showed an increased use of CEA (66·7 versus 80·1 per cent; P = 0·009). The low-risk scenario after risk score analysis demonstrated a swing towards best medical therapy (23·4 versus 57·2 per cent; P &lt; 0·001). CEA was preferred in the moderate-risk scenario and this was not altered significantly by introduction of the risk score (71·6 versus 75·6 per cent; P = 0·609). Vascular surgeons exhibited a preference towards CEA compared with stroke physicians in both low- and moderate-risk scenarios (P &lt; 0·001 and P = 0·003 respectively).

Conclusion
The addition of a risk score appeared to influence clinicians in their decision-making towards CEA in high-risk patients and towards best medical therapy in low-risk patients.
Metabolite profiling of ginsenoside Rg1 after oral administration in rat
Authors: Wang Xiaoying , Wang Chengcheng , Pu Feifei , Lin Peiyan , Qian Tianxiu 
Published: February 2014

ABSTRACTThe goal of this study is to investigate the biotransformation of ginsenoside Rg1 in vivo. A highly sensitive and specific LC‐MS/MS method was developed and used for metabolite identification in rat feces and urine after oral administration of ginsenoside Rg1. Four metabolites of Rg1 were detected in rat feces and three metabolites of Rg1 were detected in rat urine. Deglycosylation and oxygenation were found to be the major metabolic pathways of ginsenoside Rg1 after oral administration in rat. Except for the reported metabolites Rh1 and protopanaxatriol, mono‐oxygenated Rg1 and mono‐oxygenated protopanaxatriol were detected for the first time after oral administration of Rg1. The in vivo metabolite profiling of ginsenoside Rg1 in rat was proposed. Viewed collectively, Rg1 was metabolized to mono‐oxygenated Rg1, Rh1, protopanaxatriol and the secondary metabolite mono‐oxygenated protopanaxatriol in rat. Copyright © 2014 John Wiley & Sons, Ltd.
Synthesis of Aliphatic and α‐Halogenated Ketone Cyanohydrins with the Hydroxynitrile Lyase from Manihot esculenta
Authors: Diebler Johannes , von Langermann Jan , Mell Annett , Hein Martin , Langer Peter , Kragl Udo 
Published: February 2014

AbstractThe potential of the hydroxynitrile lyase from Manihot esculenta towards ketone substrates was investigated. It was observed that the length of the aliphatic chain is a key parameter for the conversion of aliphatic, non‐branched ketones. Smaller substrates are readily converted with high enantioselectivites, but the elongation of the chain length causes a significant loss in enzyme activity. For a number of halogenated, herein especially fluorinated, acetophenone derivatives the corresponding cyanohydrins have been synthesized with good to moderate enantioselectivities.
Minor Enantiomer Recycling: Application to Enantioselective Syntheses of Beta Blockers
Authors: Wen Ye‐Qian , Hertzberg Robin , Gonzalez Inanllely , Moberg Christina 
Published: February 2014

AbstractContinuous recycling of the minor product enantiomer obtained from the acetylcyanation of prochiral aldehydes provided access to highly enantiomerically enriched products. Cyanohydrin derivatives, which under normal conditions are obtained with modest or poor enantiomeric ratios, were formed with high enantiomeric purity by using a reinforcing combination of a chiral Lewis acid catalyst and a biocatalyst. The primarily obtained products were transformed into β‐adrenergic antagonists (S)‐propanolol, (R)‐dichloroisoproterenol, and (R)‐pronethalol by means of a two‐step procedure.
C,C‐ and N,C‐Coupled Dimers of 2‐Aminotetraphenylporphyrins: Regiocontrolled Synthesis, Spectroscopic Properties, and Quantum‐Chemical Calculations
Authors: Bruhn Torsten , Witterauf Franziska , Götz Daniel C. G. , Grimmer Carina T. , Würtemberger Max , Radius Udo , Bringmann Gerhard 
Published: February 2014

Abstractβ,β′‐Bisporphyrins are intrinsically chiral porphyrin dimers with fascinating properties. The configurational stability at their axes can be directed by variation of the central metal atoms. Herein, we present a regioselective functionalization of the monomeric 2‐amino‐tetraphenyl‐porphyrin as a versatile substrate for dimerization by oxidative coupling. By simple variation of the reaction conditions (solvent and oxidant), the oxidation selectively gave either the axially chiral C,C‐coupled diaminobisporphyrin in high yields or, under Ullmann conditions, the twofold N,C‐linked achiral dimer, also in good yields. A generalized mechanism for the coupling reaction is proposed based on DFT calculations. The axially chiral β,β′‐coupled porphyrin dimers were isolated as racemic mixtures, but can be resolved by HPLC on a chiral phase. TDDFT and coupled‐cluster calculations were used to explain the spectroscopic properties of the aminoporphyrins and their dimers and to elucidate the absolute configurations of the C,C‐coupled bisporphyrins.
Distance Dependence of Bidirectional Concerted Proton–Electron Transfer in Phenol‐Ru(2,2′‐bipyridine)32+ Dyads
Authors: Chen Jing , Kuss‐Petermann Martin , Wenger Oliver S. 
Published: February 2014

AbstractProton‐coupled electron transfer (PCET) was investigated in three covalent donor–bridge–acceptor molecules with different bridge lengths. Upon photoexcitation of their Ru(bpy)32+ (bpy=2,2′‐bipyridine) photosensitizer in acetonitrile, intramolecular long‐range electron transfer from a phenolic unit to Ru(bpy)32+ occurs in concert with release of the phenolic proton to pyrrolidine base. The kinetics of this bidirectional concerted proton–electron transfer (CPET) reaction were studied as a function of phenol–Ru(bpy)32+ distance by increasing the number of bridging p‐xylene units. A distance decay constant (β) of 0.67±0.23 Å−1 was determined. The distance dependence of the rates for CPET is thus not significantly steeper than that for ordinary (i.e., not proton coupled) electron transfer across the same bridges, despite the concerted motion of oppositely charged particles into different directions. Long‐range bidirectional CPET is an important reaction in many proteins and plays a key role in photosynthesis; our results are relevant in the context of photoinduced separation of protons and electrons as a means of light‐to‐chemical energy conversion. This is the first determination of β for a bidirectional CPET reaction.
Inorganic–Organic Heteropolyacid–Gold(I) Hybrids: Structures and Catalytic Applications
Authors: Hueber Damien , Hoffmann Marie , Louis Benoît , Pale Patrick , Blanc Aurélien 
Published: February 2014

AbstractGold(I)‐polyoxometalate hybrid complexes 1–4 ([PPh3AuMeCN]xH4−xSiW12O40, x=1–4) were synthesized and characterized. The structure of the primary gold(I)–polyoxometalate 1 (x=1) was fully ascertained by XRD, FTIR, 31P and 29Si magic‐angle spinning (MAS) NMR, mass spectroscopy, and SEM–energy dispersive X‐ray spectroscopy (EDX) techniques. Moreover, this complex exhibited better catalytic activity and selectivity compared with standard, homogeneous, gold catalysts in the new rearrangement of propargylic gem‐diesters.
Pd‐Catalyzed Decarboxylative Cross‐Coupling of 2‐Carboxyazine N‐Oxides with Various (Hetero)aryl Halides
Authors: Rouchet Jean‐Baptiste , Schneider Cédric , Spitz Cédric , Lefèvre Johan , Dupas George , Fruit Corinne , Hoarau Christophe 
Published: February 2014

AbstractDecarboxylative cross‐coupling reactions of substituted 2‐carboxyazine N‐oxides, with a variety of (hetero)aryl halides, by bimetallic Pd0/CuI and Pd0/AgI catalysis are reported. Two possible pathways, a conventional bimetallic‐catalyzed decarboxylative arylation, as well as a protodecarboxylative/direct CH arylation sequence have been considered. These methods provide the first general decarboxylative arylation methodology for the 2‐carboxyazine series.
Fixed‐Bed Reactor Optimization for the Synthesis of Dimethyl Ether Using a 2D Model
Authors: Zander Hans‐Jörg , Bloch Gregor , Monnin Thibaut 
Published: February 2014

AbstractDimethyl ether is typically produced from synthesis gas by conversion to methanol and subsequent etherification. Compared to this classical approach, the direct synthesis has the advantage of higher equilibrium conversion and a simpler single‐stage process. The heat release of the strongly exothermic reactions requires a careful thermal reactor design. Pure axial models are not sufficient, as they neglect the important radial heat transport resistance. Therefore, a 2D model including axial and radial gradients was implemented and used for design optimization.
In Situ Investigations of Catalytic NO Reduction Inside an Optically Accessible Flow Reactor
Authors: Zellner Alexander , Suntz Rainer , Deutschmann Olaf 
Published: February 2014

AbstractDie katalytische Reduktion von NO wurde in einem optisch zugänglichen Strömungskanal mittels planarer laserinduzierter Fluoreszenz (PLIF) in situ und nicht‐invasiv untersucht. Der Aufbau des Versuchsreaktors und dessen Adaption an die PLIF‐Methode werden präsentiert. Die Ergebnisse zeigen die zweidimensionalen Fluoreszenzverteilungen von NO über einer Katalysatorscheibe sowohl unter reaktiven als auch nicht‐reaktiven Bedingungen. Ein Pt/Al2O3‐beschichteter Monolith eines Dieseloxidationskatalysators diente dabei zur Herstellung selbstgefertigter Katalysatorscheiben.
Optimization of Catalysts for Fischer‐Tropsch Synthesis by Introduction of Transport Pores
Authors: Becker Henning , Güttel Robert , Turek Thomas 
Published: February 2014

AbstractDiffusional restrictions in the porous network of Fischer‐Tropsch catalysts strongly affect activity and product selectivity. Especially small pores hamper the diffusion of reactants. In order to overcome the diffusion restrictions, the introduction of transport pores into the catalyst and the resulting effect on reaction rate and selectivities were studied. It was shown that transport pores allow for an increase in diffusion length, maintaining high reaction rate and C5+ selectivity. Overall, the productivity can be increased through optimization of the transport pore fraction.