bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal and mechanical behavior of natural rubber latex‐silica aerogel film
Authors: On Ng Kui , Rashid Azura Abdul , Nazlan Mohd Muhid Mohd , Hamdan Halimaton 
Published: November 2011

AbstractA major problem in most natural rubber latex (NRL) commonly encountered like other polymer is susceptibility to mechanical properties and thermal degradation; particularly in thin film due to the presence of double bonds in the main chain. Therefore, it is desirable to seek for ways of improving these properties. Silica aerogel is a material with extraordinary properties was believed to have potential enhance properties in NRL films because of its high specific surface area. Therefore, based on the unique character of silica aerogel, NRL‐silica aerogel film was developed by latex compounding and dry coagulant dipping to form thin film where silica aerogel acts as filler. Silica aerogel, synthesized from rice husk was dispersed in a ball‐mill using distilled water for NRL compounding. Results indicate that increasing silica aerogel loading enhances the mechanical properties of the NRL‐silica aerogel film. Effects of postvulcanization processes were also investigated, whereby the best reinforcing effect was obtained at 4 phr silica aerogel loading with leaching postvulcanization condition. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Zur Richtlinie für die Nachrechnung von Straßenbrücken im Bestand (Nachrechnungsrichtlinie)
Authors: Marzahn Gero 
Published: November 2011

AbstractAufgrund des gestiegenen Schwerverkehrs sowie gestiegener Achs‐ und Gesamtgewichte der Fahrzeuge ist eine Nutzungsänderung für die Straßenbrücken eingetreten. Zur Sicherung der Zukunftsfähigkeit des Straßennetzes sind daher Ertüchtigungsmaßnahmen mit dem Ziel einer Tragfähigkeitsverbesserung mit üblichen Instandsetzungsmaßnahmen zu kombinieren. Eine zutreffende Bewertung der Bauwerke hinsichtlich Tragfähigkeit, Gebrauchstauglichkeit, Dauerhaftigkeit und Ermüdungssicherheit unter Berücksichtigung des vorhandenen Bauwerkzustands ist ein grundlegender Schritt dazu.Die Nachrechnungsrichtlinie soll für die Bewertung der Bauwerke einheitliche Standards, aber auch Hilfestellung vorgeben, damit Tragfähigkeit und Gebrauchstauglichkeit bestehender Straßenbrücken realistisch beurteilt werden können und die Nachrechnungsergebnisse für eine Entscheidungsfindung nachvollziehbar und vergleichbar werden.About the Provisions for evaluating necessary upgrades of older road bridgesWhile analyzing traffic volume on current German autobahns, it became obvious that the planned capacity of most highway bridges has been almost exceeded by daily traffic volume, including increasingly heavy trucks with rising numbers of axles and load size.In fact, to ensure future long‐term serviceability of the German Autobahn system, there is no way around refurbishing most of these bridges, by combining ordinary maintenance work with strengthening measures, and replacing numerous others as well. A realistic assessment of existing highway bridges that comprises bearing capacity, serviceability, and fatigue resistance in order to evaluate their structural health is a widely accepted prerequisite for a long‐lasting refurbishment strategy. The provisions reported here for evaluating necessary upgrades of older bridges provide an appropriate tool for setting uniform standards in assessing existing highway bridges to ensure comparability of results and the conclusions drawn from them.
Outcomes following surgery without radiotherapy for rectal cancer
Authors: Mathis K L , Larson D W , Dozois E J , Cima R R , Huebner M , Haddock M G , Wolff B G , Nelson H , Pemberton J H 
Published: November 2011

Abstract

Background
This study determined survival and recurrence rates following curative resection of rectal cancer without radiotherapy.

Methods
This was a retrospective review of the Mayo Clinic database of patients with rectal cancer treated with curative intent using surgery alone from 1990 to 2006. Patients who received neoadjuvant chemotherapy or radiation therapy and those who had any postoperative radiotherapy were excluded. Details were collected from the database and patient records using a protocol approved by the institutional review board.

Results
Some 655 consecutive patients with rectal cancer treated with curative intent using surgery alone were identified; 397 had stage I disease, 125 stage II and 133 stage III. Four hundred and nine patients underwent anterior resection (AR) and 246 abdominoperineal resection (APR). Median follow-up was 62 months. The 5-year rate of local recurrence was 4·3 per cent, disease-free survival 90·0 per cent and cancer-specific survival 91·5 per cent. Stage-specific and all-stage disease-free survival did not differ significantly between AR and APR. The 5-year cumulative local recurrence rate was lower following AR than APR (3·6 versus 5·5 per cent; P = 0·321). There were only two patients with positive margins and type of operation was not significant on multivariable analysis.

Conclusion
Well-performed, standardized APRs have similar local recurrence to AR. Radiation therapy may not confer much additional benefit. Copyright © 2011 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd.
Dynamic Substrate Enhancement for the Identification of Specific, Second‐Site‐Binding Fragments Targeting a Set of Protein Tyrosine Phosphatases
Authors: Schmidt Marco F. , Groves Matthew R. , Rademann Jörg 
Published: November 2011

AbstractProtein tyrosine phosphatases (PTPs) are key regulators in living systems and thus are attractive drug targets. The development of potent, selective PTP inhibitors has been a difficult challenge mainly due to the high homology of the phosphotyrosine substrate pockets. Here, a strategy of dynamic substrate enhancement is described targeting the secondary binding sites of PTPs. By screening four different PTPs from bacterial (MptpA) and human origin (PTP1B, HePtp, Shp2) with this assay, specific fragments were identified. One highly specific fragment that binds to the secondary site of Mycobacterium tuberculosis protein tyrosine phosphatase A (MptpA) was characterized in order to validate the assay concept. Finally by covalently linking the secondary fragment to a phosphotyrosine mimetic, a moderately active but highly specific inhibitor of MptpA was obtained.
Generation of a Mono‐ubiquitinated PCNA Mimic by Click Chemistry
Authors: Eger Silvia , Castrec Benoît , Hübscher Ulrich , Scheffner Martin , Rubini Marina , Marx Andreas 
Published: November 2011

AbstractGenotoxic stress results in more than 50 000 damaged DNA sites per cell per day. During DNA replication, processive high‐fidelity DNA polymerases generally stall at DNA lesions and have to be displaced by translesion synthesis DNA polymerases, which are able to bypass the lesion. This switch is mediated by mono‐ubiquitination of the processivity factor proliferating cell nuclear antigen (PCNA). To further investigate the regulation of the DNA polymerase exchange, we developed an easy and efficient method to synthesize site‐specifically mono‐ubiquitinated PCNA by click chemistry. By incorporating artificial amino acids that carry an azide (Aha) or an alkyne (Plk) in their side chains, into ubiquitin (Ub) and PCNA, respectively, we were able to link the two proteins site‐specifically by the CuI‐catalyzed azide–alkyne cycloaddition. Finally, we show that the synthetic PCNA–Ub is able to stimulate DNA synthesis by DNA polymerase δ, and that DNA polymerase η has a higher affinity for PCNA–Ub than to PCNA.
Defined Presentation of Carbohydrates on a Duplex DNA Scaffold
Authors: Schlegel Mark K. , Hütter Julia , Eriksson Magdalena , Lepenies Bernd , Seeberger Peter H. 
Published: November 2011

AbstractA new method for the spatially defined alignment of carbohydrates on a duplex DNA scaffold is presented. The use of anN‐hydroxysuccinimide (NHS)‐ester phosphoramidite along with carbohydrates containing an alkylamine linker allows for on‐column labeling during solid‐phase oligonucleotide synthesis. This modification method during solid‐phase synthesis only requires the use of minimal amounts of complex carbohydrates. The covalently attached carbohydrates are presented in the major groove of the B‐form duplex DNA as potential substrates for murine type II C‐type lectin receptors mMGL1 and mMGL2. CD spectroscopy and thermal melting revealed only minimal disturbance of the overall helical structure. Surface plasmon resonance and cellular uptake studies with bone‐marrow‐derived dendritic cells were used to assess the capability of these carbohydrate‐modified duplexes to bind to mMGL receptors.
Metal‐Ion‐Dependent Folding of a Uranyl‐Specific DNAzyme: Insight into Function from Fluorescence Resonance Energy Transfer Studies
Authors: He Ying , Lu Yi 
Published: November 2011

AbstractFluorescence resonance energy transfer (FRET) has been used to study the global folding of an uranyl (UO22+)‐specific 39E DNAzyme in the presence of Mg2+, Zn2+, Pb2+, or UO22+. At pH 5.5 and physiological ionic strength (100 mM Na+), two of the three stems in this DNAzyme folded into a compact structure in the presence of Mg2+ or Zn2+. However, no folding occurred in the presence of Pb2+ or UO22+; this is analogous to the “lock‐and‐key” catalysis mode first observed in the Pb2+‐specific 8–17 DNAzyme. However, Mg2+ and Zn2+ exert different effects on the 8–17 and 39E DNAzymes. Whereas Mg2+ or Zn2+‐dependent folding promoted 8–17 DNAzyme activity, the 39E DNAzyme folding induced by Mg2+ or Zn2+ inhibited UO22+‐specific activity. Group IIA series of metal ions (Mg2+, Ca2+, Sr2+) also caused global folding of the 39E DNAzyme, for which the apparent binding affinity between these metal ions and the DNAzyme decreases as the ionic radius of the metal ions increases. Because the ionic radius of Sr2+ (1.12 Å) is comparable to that of Pb2+ (1.20 Å), but contrary to Pb2+, Sr2+ induces the DNAzyme to fold under identical conditions, ionic size alone cannot account for the unique folding behaviors induced by Pb2+ and UO22+. Under low ionic strength (30 mM Na+), all four metal ions (Mg2+, Zn2+, Pb2+, and UO22+), caused 39E DNAzyme folding, suggesting that metal ions can neutralize the negative charge of DNA‐backbone phosphates in addition to playing specific catalytic roles. Mg2+ at low (<2 mM) concentration promoted UO22+‐specific activity, whereas Mg2+ at high (>2 mM) concentration inhibited the UO22+‐specific activity. Therefore, the lock‐and‐key mode of DNAzymes depends on ionic strength, and the 39E DNAzyme is in the lock‐and‐key mode only at ionic strengths of 100 mM or greater.
The Porosity, Acidity, and Reactivity of Dealuminated Zeolite ZSM‐5 at the Single Particle Level: The Influence of the Zeolite Architecture
Authors: Aramburo Luis R. , Karwacki Lukasz , Cubillas Pablo , Asahina Shunsuke , de Winter D. A. Matthijs , Drury Martyn R. , Buurmans Inge L. C. , Stavitski Eli , Mores Davide , Daturi Marco , Bazin Philippe , Dumas Paul , Thibault‐Starzyk Fréderic , Post Jan A. , Anderson Michael W. , Terasaki Osamu , Weckhuysen Bert M. 
Published: November 2011

AbstractA combination of atomic force microscopy (AFM), high‐resolution scanning electron microscopy (HR‐SEM), focused‐ion‐beam scanning electron microscopy (FIB‐SEM), X‐ray photoelectron spectroscopy (XPS), confocal fluorescence microscopy (CFM), and UV/Vis and synchrotron‐based IR microspectroscopy was used to investigate the dealumination processes of zeolite ZSM‐5 at the individual crystal level. It was shown that steaming has a significant impact on the porosity, acidity, and reactivity of the zeolite materials. The catalytic performance, tested by the styrene oligomerization and methanol‐to‐olefin reactions, led to the conclusion that mild steaming conditions resulted in greatly enhanced acidity and reactivity of dealuminated zeolite ZSM‐5. Interestingly, only residual surface mesoporosity was generated in the mildly steamed ZSM‐5 zeolite, leading to rapid crystal coloration and coking upon catalytic testing and indicating an enhanced deactivation of the zeolites. In contrast, harsh steaming conditions generated 5–50 nm mesopores, extensively improving the accessibility of the zeolites. However, severe dealumination decreased the strength of the Brønsted acid sites, causing a depletion of the overall acidity, which resulted in a major drop in catalytic activity.
Total Synthesis of (−)‐Brevenal: A Streamlined Strategy for Practical Synthesis of Polycyclic Ethers
Authors: Ebine Makoto , Fuwa Haruhiko , Sasaki Makoto 
Published: November 2011

AbstractWe describe a streamlined strategy for the practical synthesis of trans‐fused polycyclic ethers and its application to a concise total synthesis of (−)‐brevenal, a new pentacyclic polyether natural product with intriguing biological activities. The B‐, D‐, and E‐rings were constructed by TEMPO/PhI(OAc)2‐mediated oxidative lactonization of the corresponding 1,6‐diols, with minimal need for manipulation of oxygen functionalities. The B‐ and E‐ring lactones were appropriately functionalized by Suzuki–Miyaura coupling of lactone‐derived enol phosphates and subsequent stereoselective hydroboration. The A‐ring was formed by our mixed thioacetalization methodology. The AB‐ and DE‐ring fragments were assembled through Suzuki–Miyaura coupling, and the C‐ring was forged in the same manner as that for the A‐ring. More than two grams of the pentacyclic polyether core of (−)‐brevenal have been synthesized by the synthetic route developed in this study.
Oxidation of Zn(Cys)4 Zinc Finger Peptides by O2 and H2O2: Products, Mechanism and Kinetics
Authors: Bourlès Emilie , Isaac Manon , Lebrun Colette , Latour Jean‐Marc , Sénèque Olivier 
Published: November 2011

AbstractThe reactivity of a series of Zn(Cys)4 zinc finger model peptides towards H2O2 and O2 has been investigated. The oxidation products were identified by HPLC and ESI‐MS analysis. At pH<7.5, the zinc complexes and the free peptides are oxidised to bis‐disulfide‐containing peptides. Above pH 7.5, the oxidation of the zinc complexes by H2O2 also yields sulfinate‐ and sulfonate‐containing overoxidised peptides. At pH 7.0, monitoring of the reactions between the zinc complexes and H2O2 by HPLC revealed the sequential formation of two disulfides. Several techniques for the determination of the rate constant for the first oxidation step corresponding to the attack of H2O2 by the Zn(Cys)4 site have been compared. This rate constant can be reliably determined by monitoring the oxidation by HPLC, fluorescence, circular dichroism or absorption spectroscopy in the presence of excess ethyleneglycol bis(2‐aminoethyl ether)tetraacetic acid. In contrast, monitoring of the release of zinc with 4‐(2‐pyridylazo)resorcinol or of the thiol content with 5,5′‐dithiobis(2‐nitrobenzoate) did not yield reliable values of this rate constant for the case in which the formation of the second disulfide is slower than the formation of the first. The kinetic measurements clearly evidence a protective effect of zinc on the oxidation of the cysteines by both H2O2 and O2, which points to the fact that zinc binding diminishes the nucleophilicity of the thiolates. In addition, the reaction between the zinc finger and H2O2 is too slow to consider zinc fingers as potential sensors for H2O2 in cells.
A Stereodivergent Strategy for the Preparation of Corynantheine and Ipecac Alkaloids, Their Epimers, and Analogues: Efficient Total Synthesis of (−)‐Dihydrocorynantheol, (−)‐Corynantheol, (−)‐Protoemetinol, (−)‐Corynantheal, (−)‐Protoemetine, and Related Natural and Nonnatural Compounds
Authors: Zhang Wei , Bah Juho , Wohlfarth Andreas , Franzén Johan 
Published: November 2011

AbstractHere we present a general and common catalytic asymmetric strategy for the total and formal synthesis of a broad number of optically active natural products from the corynantheine and ipecac alkaloid families, for example, indolo[2,3‐a]‐ and benzo[a]quinolizidines. Construction of the core alkaloid skeletons with the correct absolute and relative stereochemistry relies on an enantioselective and diastereodivergent one‐pot cascade sequence followed by an additional diastereodivergent reaction step. This allows for enantio‐ and diastereoselective synthesis of three out of four possible epimers of the quinolizidine alkaloids that begin from common and easily accessible starting materials by using a common synthetic route. Focus has been made on excluding protecting groups and limiting isolation and purification of synthetic intermediates. This methodology is applied in the total synthesis of the natural products (−)‐dihydrocorynantheol, (−)‐hirsutinol, (−)‐corynantheol, (−)‐protometinol, (−)‐dihydrocorynantheal, (−)‐corynantheal, (−)‐protoemetine, (−)‐(15S)‐hydroxydihydrocorynantheol, and an array of their nonnatural epimers. The potential of this strategy is also demonstrated in the synthesis of biologically interesting natural product analogues not accessible through synthetic elaboration of alkaloid precursors available from nature, for example, thieno[3,2‐a]quinolizidine derivatives. We also report the formal synthesis of (+)‐dihydrocorynantheine, (−)‐emetine, (−)‐cephaeline, (−)‐tubulosine, and (−)‐deoxytubulosine.
Highly Enantioselective Synthesis of Tertiary Boronic Esters and their Stereospecific Conversion to other Functional Groups and Quaternary Stereocentres
Authors: Scott Helen K. , Aggarwal Varinder K. 
Published: November 2011

AbstractOrganoboron compounds are useful in asymmetric synthesis. We have developed an efficient methodology for the highly enantioselective synthesis of tertiary boronic esters from the corresponding secondary benzylic alcohols. Further stereospecific transformations of the boronic ester moiety are described including the preparation of tertiary alcohols, C‐tertiary amines and tertiary arylalkanes. Several homologations of tertiary boronic esters have also been developed for the construction of quaternary stereocentres.
Enantioselective IrI‐Catalyzed Carbocyclization of 1,6‐Enynes by the Chiral Counterion Strategy
Authors: Barbazanges Marion , Augé Mylène , Moussa Jamal , Amouri Hani , Aubert Corinne , Desmarets Christophe , Fensterbank Louis , Gandon Vincent , Malacria Max , Ollivier Cyril 
Published: November 2011

AbstractEnantioenriched bicyclo[4.1.0]hept‐2‐enes were synthesized by IrI‐catalyzed carbocyclization of 1,6‐enynes. No chiral ligands were used, CO and PPh3 were the only ligands bound to iridium. Instead, the stereochemical information was localized on the counterion of the catalyst, generated in situ by reaction of Vaska’s complex (trans‐[IrCl(CO)(PPh3)2]) with a chiral silver phosphate. Enantiomeric excesses up to 93 % were obtained when this catalytic mixture was used. 31P NMR and IR spectroscopy suggest that formation of the trans‐ [Ir(CO)(PPh3)2]+ moiety occurs by chlorine abstraction. Moreover, density functional theory calculations support a 6‐endo‐dig cyclization promoted by this cationic moiety. The chiral phosphate anion (OP*) controls the enantioselectivity through formation of a loose ion pair with the metal center and establishes a CH⋅⋅⋅OP* hydrogen bond with the substrate. This is a rare example of asymmetric counterion‐directed transition‐metal catalysis and represents the first application of such a strategy to a CC bond‐forming reaction.
ChemInform Abstract: Rational Design of Complex Borides — One‐Electron‐Step Evolution from Soft to Semi‐Hard Itinerant Ferromagnets in the New Boride Series Ti2FeRu5‐nRhnB2 (1 ≤ n ≤ 5).
Authors: Fokwa Boniface P. T. , Lueken Heiko , Dronskowski Richard 
Published: November 2011

AbstractThe new series of title compounds is prepared by arc melting of stoichiometric mixtures of the elements and characterized by XRD and magnetic measurements.
ChemInform Abstract: Water Exchange Reactivity and Stability of Cobalt Polyoxometalates under Catalytically Relevant pH Conditions: Insight into Water Oxidation Catalysis.
Authors: Lieb Dominik , Zahl Achim , Wilson Elizabeth F. , Streb Carsten , Nye Leanne C. , Meyer Karsten , Ivanovic‐Burmazovic Ivana 
Published: November 2011

AbstractWater exchange on the Co centers in Na10 [Co4(H2O)2 (α‐PW9O34)2] (I) in the catalytically relevant pH region between 6 and 10 is investigated by 17O NMR spectroscopy and ultrahigh‐resolution electrospray ionization mass spectrometry to gain insight into the elementary reaction steps involved in the overall water oxidation process.
ChemInform Abstract: Structure Refinement and Magnetic Properties of Ce2RuAl3 and a Group‐Subgroup Scheme for Ce5Ru3Al2.
Authors: Mishra Trinath , Hoffmann Rolf‐Dieter , Schwickert Christian , Poettgen Rainer 
Published: November 2011

AbstractCe2RuAl3 is prepared by high‐frequency melting of the elements in a sealed tantalum tube followed by annealing at 1070 K for 4 h.
ChemInform Abstract: Benzylic‐Acetoxylation of Alkylbenzenes with PhI(OAc)2 in the Presence of Catalytic Amounts of TsNH2 and I2
Authors: Baba Haruka , Moriyama Katsuhiko , Togo Hideo 
Published: November 2011

AbstractThe introduction of an acetoxy or benzoyloxy group to the benzylic position of alkylbenzenes is achieved using hypervalent iodine compounds (II) in the presence of iodine and sulfonamides.
ChemInform Abstract: sp3 C—H Bond Activation with Ruthenium(II) Catalysts and C(3)‐Alkylation of Cyclic Amines.
Authors: Sundararaju Basker , Achard Mathieu , Sharma Gangavaram V. M. , Bruneau Christian 
Published: November 2011

AbstractN‐Protected cyclic amines are regioselectively alkylated at the 3‐position by reaction with aromatic or aliphatic aldehydes using an optimized catalytic system.
ChemInform Abstract: Synthesis of Bi‐ and Tetracatenar Highly Fluorinated Compounds for Grafting on Silicone Materials.
Authors: Malfait Stephane , Gerard Stephane , Plantier‐Royon Richard , Mignani Gerard , Portella Charles 
Published: November 2011

AbstractThe preparation of several new compounds containing up to four perfluorooctyl chains is reported.
ChemInform Abstract: Stereoselective Synthesis of Functionalized Cyclopropane Derivatives via α‐Thiocyanate Ketone‐Based Three‐Component Reaction.
Authors: Wu Fei‐Yue , Li Ying , Feng Hui , Wu Qiong , Jiang Bo , Shi Feng , Tu Shu‐Jiang 
Published: November 2011

AbstractA direct one‐pot method allows the synthesis of spiro‐substituted as well as polysubstituted trans‐cyclopropanes in a highly diastereoselective manner.
ChemInform Abstract: Synthesis of Internal Fluorinated Alkenes via Facile Aryloxylation of Substituted Phenols with Aryl Trifluorovinyl Ethers.
Authors: Moody Justin D. , VanDerveer Don , Smith Dennis W. Jr. , Iacono Scott T. 
Published: November 2011

AbstractThe reaction affords vinyl substitution products as (E)/(Z)‐mixtures if NaH is used as base.
ChemInform Abstract: Effect of High Pressure on the Organocatalytic Asymmetric Michael Reaction: Highly Enantioselective Synthesis of γ‐Nitroketones with Quaternary Stereogenic Centers.
Authors: Kwiatkowski Piotr , Dudzinski Krzysztof , Lyzwa Dawid 
Published: November 2011

AbstractHydrostatic pressure is essential to achieve the synthesis of various cyclic nitroketones with high yields and excellent enantioselectivities.
ChemInform Abstract: Copper/Oxalohydrazide/Ketone Catalyzed Synthesis of Primary Arylamines via Coupling of Aryl Halides with Aqueous Ammonia in Water.
Authors: Li Ying , Zhu Xinhai , Meng Fei , Wan Yiqian 
Published: November 2011

AbstractThe reactions can also be carried out at room temperature, albeit with prolonged reaction times from one to several days.
ChemInform Abstract: Switching of Enantioselectivity in the Catalytic Addition of Diethylzinc to Aldehydes by Regioisomeric Chiral 1,3‐Amino Sulfonamide Ligands.
Authors: Hirose Takuji , Sugawara Kazuyuki , Kodama Koichi 
Published: November 2011

AbstractThe 1,3‐amino sulfonamides efficiently promote the asymmetric addition of ZnEt2 to various aldehydes.
ChemInform Abstract: A Recyclable Fluorous Thiourea Organocatalyst for the Chemoselective Oxidation of Sulfides.
Authors: Huang Yi‐Bo , Yi Wen‐Bin , Cai Chun 
Published: November 2011

AbstractA diphenylthiourea with a fluorinated side chain is shown to be an efficient catalyst for the chemoselective oxidation of sulfides to sulfoxides.