bluuebunny/crossref_metadata_2025_split huggingface dataset:
Asymmetric aza‐Diels–Alder and Cation–olefin Cyclization Sequence: a Concise Way to Fused Chiral Cyclopenta[b]piperidines
Authors: Li Qing‐Zhu , Ma Lei , Dong Lin , Chen Ying‐Chun 
Published: April 2012

AbstractAn asymmetric aza‐Diels–Alder and cation–olefin cyclization sequence has been developed to construct cyclopenta[b]piperidine skeletons with moderate yields and excellent stereoselectivities, by employing 5‐enals and N‐Ts‐1‐aza‐1,3‐butadienes as the starting materials. A designed domino cation–olefin/Friedel–Crafts reaction verified that the cyclization of N‐Ts iminium ion underwent a stepwise cationic process.
Optimization of the Biotechnological Process for Hide Unhairing in Substitution of Toxic Sulfides
Authors: Dettmer A. , Coelho Cavalheiro J. , Cavalli É. , Misturini Rossi D. , de Souza Gusatti C. , Záchia Ayub M. A. , Gutterres M. 
Published: April 2012

AbstractScreening and isolation of a new Bacillus subtilis strain and production of its proteases for leather unhairing are described. B. subtilis strain BLBc 11 was isolated from the aerobic sludge of a tannery. Optimization of enzyme production by this bacterium was carried out using the Plackett‐Burman and central composite design. Unhairing and inter‐fibrillary removal capabilities were evaluated by scanning electron microscopy and determination of proteoglycans and glycosaminoglycans. Crude enzymatic extracts of B. subtilis BLBc 11 cultures were applied for the unhairing process of hides with excellent results, suggesting that this safe enzymatic preparation can replace the toxic chemicals commonly used in this process.
Recent Developments in the Synthesis of Five‐ and Six‐Membered Heterocycles Using Molecular Iodine
Authors: Parvatkar Prakash T. , Parameswaran Perunninakulath S. , Tilve Santosh G. 
Published: April 2012

AbstractHeterocyclic scaffolds represent the key structural subunits of many biologically active compounds. Over the last few years iodine‐mediated reactions have been extensively studied due to their low cost and eco‐friendliness. This Review covers advances in the field of iodine‐mediated synthesis of heterocyclic compounds since 2006, especially with an emphasis on mechanisms of ring formation. In this article, syntheses of different heterocycles are classified based on the manipulation of functional groups.
Sulfangolids, Macrolide Sulfate Esters from Sorangium cellulosum
Authors: Zander Wiebke , Irschik Herbert , Augustiniak Hermann , Herrmann Martina , Jansen Rolf , Steinmetz Heinrich , Gerth Klaus , Kessler Wolfgang , Kalesse Markus , Höfle Gerhard , Müller Rolf 
Published: April 2012

AbstractSulfangolids are the first sulfate ester containing secondary metabolites from myxobacteria. The metabolites 1–4 and the structurally related kulkenon (5) were isolated from different strains of the species Sorangium cellulosum. In the course of isolation all metabolites proved to be rather sensitive due to their conjugated double bond systems and the strong acidic nature of the sulfate ester in sulfangolids. The relative configuration of sulfangolid C (3) was assigned by extensive 1D and 2D NMR analysis and molecular modelling. In addition, the biosynthesis of 3 was studied by feeding experiments.
From Composites to Solid Solutions: Modeling of Ionic Conductivity in the CaF2–BaF2 System
Authors: Zahn Dirk , Heitjans Paul , Maier Joachim 
Published: April 2012

AbstractBy using calcium fluorite and barium fluorite as test materials, we demonstrated that homovalent “dopants” can greatly affect ionic conductivity through locally changing the defect density. Whilst this doping is a state‐of‐the‐art effect in the case of dopants that replace native ions of different charge (heterovalent dopants), it is a rather surprising effect at a first glance for substitutional dopants of the same charge; here, the phenomenon is not electrostatic, but elastic in nature. As a consequence of size mismatch, the smaller Ca atoms in the BaF2 lattice favored the formation of interstitial sites that were located close to the Ca atoms, whilst doping larger Ba species into the CaF2 phase favored vacancy formation. In terms of conductivity, and in agreement with the different mobilities, the first doping effect was favorable, whilst the other decreased conductivity. The concentration effects were formalized by a heterogeneous Frenkel reaction that was distinguished from the mean Frenkel reaction by additional (elastic) trapping that became more pronounced the lower the temperature. It was very revealing to relate this phenomenon to CaF2–BaF2 multilayers and composites. In very general terms, these effects in the solid solutions were understood as being the atomistic limit of the interfacial charge‐transfer that occurred at the hetero‐interface of the crystallites or films, and reflected the transition from heterogeneous doping (higher‐dimensional doping) to homogeneous doping (zero‐dimensional doping).
Formation of Columnar Liquid Crystals on the Basis of Unconventional Triazine‐Based Dendrimers by the C3‐Symmetric Approach
Authors: Lai Long‐Li , Hsu Shun‐Ju , Hsu Hui‐Chu , Wang Sheng‐Wei , Cheng Kung‐Lung , Chen Chun‐Jung , Wang Tsai‐Hui , Hsu Hsiu‐Fu 
Published: April 2012

AbstractTwo series of unconventional triazine‐based dendrimers with C2 symmetry and C3 symmetry were prepared. The newly prepared C3‐symmetrical dendrimers were characterized by 1H and 13C NMR spectroscopy, mass spectrometry, and elemental analysis. Differential scanning calorimetry, polarizing microscopy, and powder XRD showed that the C3‐symmetrical dendrimers display columnar liquid‐crystalline phases during thermal treatment, but the C2‐symmetrical dendrimers were not observed to behave correspondingly. The molecular conformations of C3‐ and C2‐symmetrical dendrimers were obtained by computer simulation with the MM2 model of the CaChe program in the gas phase. The simulation results reasonably explain the different mesogenicities of C3‐ and C2‐symmetric dendrimers. This new strategy should be applicable to other types of unconventional dendrimers with rigid frameworks for displaying columnar liquid‐crystalline behavior.
Gold‐Catalyzed 1,2‐/1,2‐Bis‐acetoxy Migration of 1,4‐Bis‐propargyl Acetates: A Mechanistic Study
Authors: de Haro Teresa , Gómez‐Bengoa Enrique , Cribiú Riccardo , Huang Xiaogen , Nevado Cristina 
Published: April 2012

AbstractThe late transition metal catalyzed rearrangement of propargyl acetates offers an interesting platform for the development of synthetically useful transformations. We have recently shown that gold complexes can catalyze a highly selective tandem 1,2‐/1,2‐bis‐acetoxy migration in 1,4‐bis‐propargyl acetates to form 2,3‐bis‐acetoxy‐1,3‐dienes. In this way, (1Z,3Z)‐ or (1Z,3E)‐ and (1E,3Z)‐1,3‐dienes could be obtained in a stereocontrolled manner depending on the electronic and steric features of the ancillary ligand bound to gold and the substituents at the propargylic positions. In this work, we report an experimental study on the scope of this transformation, plus a detailed theoretical examination of the reaction mechanism, which has revealed the key features responsible for the reaction stereoselectivity. Synthetic applications towards the one‐pot synthesis of quinoxaline heterocycles and tandem Diels–Alder processes have also been devised.
Rare‐Earth Nanoparticles with Enhanced Upconversion Emission and Suppressed Rare‐Earth‐Ion Leakage
Authors: Wang Ye‐Fu , Sun Ling‐Dong , Xiao Jia‐Wen , Feng Wei , Zhou Jia‐Cai , Shen Jie , Yan Chun‐Hua 
Published: April 2012

AbstractUpconversion emissions from rare‐earth nanoparticles have attracted much interest as potential biolabels, for which small particle size and high emission intensity are both desired. Herein we report a facile way to achieve NaYF4:Yb,Er@CaF2 nanoparticles (NPs) with a small size (10–13 nm) and highly enhanced (ca. 300 times) upconversion emission compared with the pristine NPs. The CaF2 shell protects the rare‐earth ions from leaking, when the nanoparticles are exposed to buffer solution, and ensures biological safety for the potential bioprobe applications. With the upconversion emission from NaYF4:Yb,Er@CaF2 NPs, HeLa cells were imaged with low background interference.
Expanding the Chemistry of Cationic N‐Heterocyclic Carbenes: Alternative Synthesis, Reactivity, and Coordination Chemistry
Authors: Hildebrandt Björn , Raub Stephan , Frank Walter , Ganter Christian 
Published: April 2012

AbstractA new synthetic route to complexes of the cationic N‐heterocyclic carbene ligand 2 has been developed by the attachment of a cationic pentamethylcyclopentadienylruthenium ([RuCp*]+) fragment to a metal‐coordinated benzimidazol‐2‐ylidene ligand. The coordination chemistry and the steric and electronic properties of the cationic carbene were investigated in detail by experimental and theoretical methods. X‐ray structures of three carbene–metal complexes were determined. The cationic ligand 2 is a poorer overall electron donor relative to the related neutral carbene, which is evident from cyclic voltammetry (CV) and IR measurements.
Controlled Bimodal Molecular‐Weight‐Distribution Polymers: Facile Synthesis by RAFT Polymerization
Authors: Qin Jian , Zhang Lifen , Jiang Hongjuan , Zhu Jian , Zhang Zhengbiao , Zhang Wei , Zhou Nianchen , Cheng Zhenping , Zhu Xiulin 
Published: April 2012

AbstractThe RAFT agents RAFT‐1 and RAFT‐2 were used for RAFT polymerization to synthesize well‐defined bimodal molecular‐weight‐distribution (MWD) polymers. The system showed excellent controllability and “living” characteristics toward both the higher‐ and lower‐molecular‐weight fractions. It is important that bimodal higher‐molecular‐weight (HMW) polymers and block copolymers with both well‐controlled molecular weight (MW) and MWD could be prepared easily due to the “living” features of RAFT polymerization. The strategy realized a mixture of higher/lower‐molecular‐weight polymers at the molecular level but also preserved the features of living radical polymerization (LRP) of the RAFT polymerization.
Ion‐Pair Recognition of Tetramethylammonium Salts by Halogenated Resorcinarenes
Authors: Beyeh N. Kodiah , Weimann Dominik P. , Kaufmann Lena , Schalley Christoph A. , Rissanen Kari 
Published: April 2012

AbstractThe non‐covalent interactions of different upper‐rim‐substituted C2‐resorcinarenes with tetramethylammonium salts were analyzed in the gas phase in an Electrospray Ionization Fourier‐transform ion‐cyclotron‐resonance (ESI‐FTICR) mass spectrometer and by 1H NMR titrations. The order of binding strengths of the hosts towards the tetramethylammonium cation in the gas phase reflects the electronic nature of the substituents on the upper rim of the resorcinarene. In solution, however, a different trend with particularly high binding constants for halogenated resorcinarenes has been observed. This trend can be explained by a synergetic effect originating from the interaction of the halogenated resorcinarenes with the counter anions through hydrogen bonding. This study highlights the importance of weak interactions in recognition processes and points out the benefits of comparing the gas‐phase data with results obtained from solution experiments.
Molecular Recognition of T:G Mismatched Base Pairs in DNA as Studied by Electrospray Ionization Mass Spectrometry
Authors: Riccardi Sirtori Federico , Aldini Giancarlo , Colombo Maristella , Colombo Nicoletta , Malyszko Jan , Vistoli Giulio , D'Alessio Roberto 
Published: April 2012

AbstractPostreplicative mismatch repair (MMR) is a cellular system involved in the recognition and correction of DNA polymerase errors that escape detection in proofreading. Of the various mismatched bases, T:G pairing in DNA is one of the more common mutations leading to the formation of tumors in humans. In addition, the absence of the MMR system can generate resistance to several chemotherapeutic agents, particularly DNA‐damaging substances. The main purpose of this study was the setup and validation of an electrospray ionization (ESI) mass spectrometry method for the identification of small molecules that are able to recognize T:G mismatches in DNA targets. These findings could be useful for the discovery of new antitumor drugs. The analytical method is based on the ability of electrospray to preserve the noncovalent adducts present in solution and transfer them to the gas phase. Lexitropsin derivatives (polyimidazole compounds) have been previously described as selective for T:G mismatch binding by NMR and ITC studies. We synthesized and tested various polyimidazole derivatives, one of which in particular (NMS‐057) showed a higher affinity for an oligonucleotide DNA sequence containing a T:G mismatched base pair. To rationalize these findings, molecular docking studies were performed using available NMR structures. Moreover, ESI‐MS experiments, performed on an orbitrap mass spectrometer, highlighted the formation of heterodimeric complexes between DNA sequences, distamycin A, and polyimidazole compounds. Our results confirm that this ESI method could be a valuable tool for the identification of new molecules able to specifically recognize T:G mismatched base pairs.
Depression in Early, Middle and Late Adolescence: Differential Evidence for the Cognitive Diathesis–Stress Model
Authors: Braet Caroline , Vlierberghe Leen Van , Vandevivere Eva , Theuwis Lotte , Bosmans Guy 
Published: April 2012

Cognitive theory is a prominent framework to study depression in both adults and adolescents. This theory stated that dysfunctional schemas are moderators (known as diathesis) in the association of current stress and psychopathology. However, in adolescents, less evidence has been found so far to corroborate the importance of these schemas. This study aimed to investigate in a cross‐sectional design the moderating role of adolescents' early maladaptive schemas (EMS) on depressive symptoms. This will be studied in relation to both important daily stressors (i.e., maternal, paternal and peer rejection) and stressful life events.METHODAdolescents (N = 228, age 12–18 years), selected from inpatient and outpatient clinical settings and a non‐referred sample, completed questionnaires and interviews measuring psychopathology, cognitive schemas, peer rejection, maternal and paternal rejection, and stressful life events. Parents completed questionnaires about their adolescent measuring psychopathology, stressful life events and peer rejection, as well as their own parental behaviour.RESULTSCorrelational analyses revealed significant associations between the study variables. Evidence was found for an interaction effect between the adolescents' EMS and peer rejection in explaining depressive symptoms, but only in late adolescents. Copyright © 2012 John Wiley & Sons, Ltd.Key Practitioner Message

Stress induced by maternal and, in lesser extent, paternal rejection is contributing to depressive symptoms primarily in younger and to lesser extent in older age groups.
The quality of peer relationships becomes an increasingly salient source of distress as adolescence unfolds and is certainly an important mechanism affecting depression in adolescence.
Maladaptive schemas only start functioning as a cognitive diathesis in late adolescence, increasing depression in response to peer‐related distress.
Since maladaptive schemas are not yet operating as cognitive vulnerability factors in early and middle adolescence, early interventions for depressive disorders may be more effective compared with treatment in later adolescence.
Structural, electrical, thermal and optical properties of the nonlinear optical crystal L‐Arginine Fluoride
Authors: Mohandoss R. , Dhanuskodi S. , Jayalakshmy M. S. , Philip J. , Bhagavannarayana G. 
Published: April 2012

AbstractSingle crystals of L‐Arginine Fluoride (LAF) have been grown by the slow evaporation technique, and the crystalline perfection was studied by HRXRD. Optical absorption studies reveal the lower cut off wavelength (280 nm) and the band gap (5.1 eV). The dielectric constant and dielectric loss have been measured as a function of frequency (42 Hz–5 MHz) and temperature (307‐368K) and the activation energy is 77 μeV. The thermal transport properties such as thermal conductivity (0.88 ± 0.02 W/mK) and specific heat capacity (482±24 J/kg/K) have been estimated by the photopyroelectric technique. The nonlinear refractive index n2, is found to be of the order of 10−13 cm2/W by the Z‐scan technique.
A myelin gene causative of a catatonia‐depression syndrome upon aging
Authors: Hagemeyer Nora , Goebbels Sandra , Papiol Sergi , Kästner Anne , Hofer Sabine , Begemann Martin , Gerwig Ulrike C. , Boretius Susann , Wieser Georg L. , Ronnenberg Anja , Gurvich Artem , Heckers Stephan H. , Frahm Jens , Nave Klaus‐Armin , Ehrenreich Hannelore 
Published: April 2012

AbstractSevere mental illnesses have been linked to white matter abnormalities, documented by postmortem studies. However, cause and effect have remained difficult to distinguish. CNP (2′,3′‐cyclic nucleotide 3′‐phosphodiesterase) is among the oligodendrocyte/myelin‐associated genes most robustly reduced on mRNA and protein level in brains of schizophrenic, bipolar or major depressive patients. This suggests that CNP reduction might be critical for a more general disease process and not restricted to a single diagnostic category. We show here that reduced expression of CNP is the primary cause of a distinct behavioural phenotype, seen only upon aging as an additional ‘pro‐inflammatory hit’. This phenotype is strikingly similar in Cnp heterozygous mice and patients with mental disease carrying the AA genotype at CNP SNP rs2070106. The characteristic features in both species with their partial CNP ‘loss‐of‐function’ genotype are best described as ‘catatonia‐depression’ syndrome. As a consequence of perturbed CNP expression, mice show secondary low‐grade inflammation/neurodegeneration. Analogously, in man, diffusion tensor imaging points to axonal loss in the frontal corpus callosum. To conclude, subtle white matter abnormalities inducing neurodegenerative changes can cause/amplify psychiatric diseases.
State of the art of the bioliq® process for synthetic biofuels production
Authors: Dahmen Nicolaus , Dinjus Eckhard , Kolb Thomas , Arnold Ulrich , Leibold Hans , Stahl Ralph 
Published: April 2012

AbstractSynthetic fuels from biomass (also referred to as BTL, biomass to liquids) may contribute to the future motor fuel consumption to a considerable extent. To overcome the logistical hurdles connected with the industrial use of large quantities of biomass, the de‐central‐centralized bioliq® concept has been developed. It is based on a regional pretreatment of biomass for energy densification by fast pyrolysis. The intermediate referred to as biosyncrude allows for economic long‐range transportation. Collected from a number of those plants, the biosyncrude is converted into synthesis gas, which is cleaned, conditioned, and further converted to fuels or chemicals in an industrial plant complex of reasonable size. Gasification is performed in a high‐pressure entrained flow gasifier at pressures adjusted to those of the subsequently following chemical syntheses. For increased fuel flexibility and conversion of ash rich feed materials, the gasifier is equipped with a cooling screen operated in slagging mode. At Karlsruhe Institute of Technology (KIT), a pilot plant has been erected for process demonstration along the whole process chain. The two MWth fast pyrolysis plant is already in operation since 2009; the five MWth gasifier, the hot gas cleaning section, and a gasoline synthesis via dimethylether are to be finished in 2011. Commissioning of that plant complex will follow in 2012. The technology applied in the bioliq® process chain and on the state of construction of the pilot plant is presented. © 2012 American Institute of Chemical Engineers Environ Prog, 2012
The logistic and construction challenges of an autobahn tunnel with only one accessible portal / Logistische und bautechnische Herausforderungen eines Autobahntunnels mit nur einem zugänglichen Portal
Authors: Balmer Olivier 
Published: April 2012

AbstractThe Graitery Tunnel is about 2.5 km long and lies on the route of the A16 autobahn through the Jura Mountains. It was originally planned to excavate the tunnel from both portals, but geological problems at the south portal have delayed the drive from that end for years. A new logistic plan was required for inner lining and tunnelling. A mobile bridge construction over 60 m long was used in the tunnel, which made it possible to start the lining works while tunnelling was still underway. Due to newly available geological information, the structural calculations for the south drive and the tunnelling scheme were checked. The latter was thoroughly revised with a change to partial‐face excavation in five stages. Although some works will now be completed years later than planned, the tunnel will be handed over to the client for fitting out with not even one and a half years of delay against the original schedule.Der Tunnel Graitery ist ein rund 2,5 km langer Autobahntunnel der Transjuranne A16. Geplant war, den Tunnel von beiden Portalen her auszubrechen. Geologische Probleme im Bereich des Südportals haben den Gegenvortrieb um Jahre verzögert. Ein neues Logistikkonzept für Innenausbau und Vortrieb war erforderlich. Im Tunnel wurde eine über 60 m lange selbst fahrende Brückenkonstruktion installiert, welche es erlaubte, während des Vortriebs mit dem Innenausbau zu beginnen. Aufgrund neuer geotechnischer Kenntnisse wurden die statischen Berechnungen des Südvortriebs und das Vortriebkonzept überprüft. Letzteres wurde komplett überarbeitet und zu Gunsten eines Teilausbruchs in fünf Etappen geändert. Obwohl einzelne Arbeiten Jahre später als geplant fertig gestellt wurden, wird der Tunnel mit nicht einmal eineinhalb Jahren Verzögerung gegenüber dem ursprünglichen Bauprogramm dem Bauherrn für die Ausrüstungsarbeiten übergeben.
Development and Testing of a New Computerized Link Analysis System
Authors: Zhao Y. , Hignett S. , Mansfield N. J. 
Published: April 2012

AbstractLink analysis (LA) is a popular ergonomic tool for studying and improving the layout of workspaces. It uses a data (event) recording method to input interactions of human behavior with their environment. The traditional “pen and paper'' method of LA is cumbersome, time consuming, and gives limited outputs. To address these limitations, the computerized link analysis (CLA) system was developed and tested in laboratory and real‐world environments. CLA offers an integrated task analysis tool, including traditional LA functions (layout, event recording) with more detail for operator activities, time‐motion functions, and multioperator data recording. As well as the conventional LA results (link diagrams and link tables), there are additional outputs for time‐event lists (start/end time, duration, chronology, additional notes, importance, and operator ID), and processed link diagrams with the link direction and frequency. © 2012 Wiley Periodicals, Inc.