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111.
Peter C. Roozemond Martin van Drongelen Zhe Ma Anne B. Spoelstra Daniel Hermida‐Merino Gerrit W. M. Peters 《Macromolecular rapid communications》2015,36(4):385-390
Flow‐induced structure formation is investigated with in situ wide‐angle X‐ray diffraction with high acquisition rate (30 Hz) using isotactic polypropylene in a piston‐driven slit flow with high wall shear rates (up to ≈900 s−1). We focus on crystallization within the shear layers that form in the high shear rate regions near the walls. Remarkably, the kinetics of the crystallization process show no dependence on either flow rate or flow time; the crystallization progresses identically regardless. Stronger or longer flows only increase the thickness of the layers. A conceptual model is proposed to explain the phenomenon. Above a certain threshold, the number of shish‐kebabs formed affects the rheology such that further structure formation is halted. The critical amount is reached already within 0.1 s under the current flow conditions. The change in rheology is hypothesized to be a consequence of the “hairy” nature of shish. Our results have large implications for process modelling, since they suggest that for injection molding type flows, crystallization kinetics can be considered independent of deformation history.
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Aubert B Barate R Bona M Boutigny D Couderc F Karyotakis Y Lees JP Poireau V Tisserand V Zghiche A Grauges E Palano A Chen JC Qi ND Rong G Wang P Zhu YS Eigen G Ofte I Stugu B Abrams GS Battaglia M Brown DN Button-Shafer J Cahn RN Charles E Gill MS Groysman Y Jacobsen RG Kadyk JA Kerth LT Kolomensky YG Kukartsev G Lynch G Mir LM Orimoto TJ Pripstein M Roe NA Ronan MT Wenzel WA del Amo Sanchez P Barrett M Ford KE Harrison TJ Hart AJ Hawkes CM Morgan SE Watson AT Held T Koch H Lewandowski B 《Physical review letters》2007,98(5):051802
We present an observation of B-->eta'K*. The data sample corresponds to 232x10(6) BB[over ] pairs collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the Stanford Linear Accelerator Center. We measure the branching fractions (in units of 10(-6)) B(B(0)-->eta'K*0)=3.8+/-1.1+/-0.5 and B(B+-->eta'K*+)=4.9(1.7)(+1.9)+/-0.8, where the first error is statistical and the second systematic. A simultaneous fit results in the observation of B-->eta'K* with B(B-->eta'K*)=4.1(-0.9)(+1.0)+/-0.5. We also search for B-->eta'rho and eta'f(0)(980)(f(0)-->pi+pi-) with results and 90% confidence level upper limits B(B+-->eta'rho+)=8.7(-2.8-1.3)(+3.1+2.3) (<14), B(B(0)-->eta'rho0)<3.7, and B(B(0)-->eta'f(0)(980)(f(0)-->pi+pi-))<1.5. Charge asymmetries in the channels with significant yields are consistent with zero. 相似文献
114.
Matthias Krumb Dr. Maximilian Jäger Alice Voss Loreen Immig Dr. Karin Peters Danuta Kowalczyk Prof. Dr. Albrecht Bufe Prof. Dr. Till Opatz Prof. Dr. Otto Holst Prof. Dr. Christian Vogel Dr. Marcus Peters 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(3):928-933
Arabinogalactan, a microheterogeneous polysaccharide occurring in plants, is known for its allergy-protective activity, which could potentially be used for preventive allergy treatment. New treatment options are highly desirable, especially in a preventive manner, due to the constant rise of atopic diseases worldwide. The structural origin of the allergy-protective activity of arabinogalactan is, however, still unclear and isolation of the polysaccharide is not feasible for pharmaceutical applications due to a variation of the activity of the natural product and contaminations with endotoxins. Therefore, a pentasaccharide partial structure was selected for total synthesis and subsequently coupled to a carrier protein to form a neoglycoconjugate. The allergy-protective activity of arabinogalactan could be reproduced with the partial structure in subsequent in vivo experiments. This is the first example of a successful simplification of arabinogalactan with a single partial structure while retaining its allergy-preventive potential. 相似文献
115.
C. Amsler F. H. Heinsius H. Koch B. Kopf U. Kurilla C. A. Meyer K. Peters J. Pychy M. Steinke U. Wiedner 《The European Physical Journal C - Particles and Fields》2015,75(3):124
The spin density matrix of the \(\omega \) has been determined for the reaction \({\bar{p}p}\,\rightarrow \,\omega \pi ^0\) with unpolarized in-flight data measured by the Crystal Barrel LEAR experiment at CERN. The two main decay modes of the \(\omega \) into \(\pi ^0 \gamma \) and \(\pi ^+ \pi ^- \pi ^0\) have been separately analyzed for various \({\bar{p}}\)momenta between 600 and 1940 MeV/c. The results obtained with the usual method by extracting the matrix elements via the \(\omega \) decay angular distributions and with the more sophisticated method via a full partial wave analysis are in good agreement. A strong spin alignment of the \(\omega \) is clearly visible in this energy regime and all individual spin density matrix elements exhibit an oscillatory dependence on the production angle. In addition, the largest contributing orbital angular momentum of the \({\bar{p}p~}\)system has been identified for the different beam momenta. It increases from \(L^{max}_{{\bar{p}p~}}\) \(=\) 2 at 600 MeV/c to \(L^{max}_{{\bar{p}p~}}\) \(=\) 5 at 1940 MeV/c. 相似文献
116.
Enzymatic Conversion of Flavonoids using Bacterial Chalcone Isomerase and Enoate Reductase 下载免费PDF全文
Dipl.‐Biol. Mechthild Gall Dipl.‐Biochem. Maren Thomsen Dipl.‐Biochem. Christin Peters Dr. Ioannis V. Pavlidis M. Sc. Patrick Jonczyk M. Sc. Philipp P. Grünert Dr. Sascha Beutel Prof. Dr. Thomas Scheper Egon Gross Dr. Michael Backes Dr. Torsten Geißler Dr. Jakob P. Ley Dr. Jens‐Michael Hilmer Dr. Gerhard Krammer Dr. Gottfried J. Palm Prof. Dr. Winfried Hinrichs Prof. Dr. Uwe T. Bornscheuer 《Angewandte Chemie (International ed. in English)》2014,53(5):1439-1442
Flavonoids are a large group of plant secondary metabolites with a variety of biological properties and are therefore of interest to many scientists, as they can lead to industrially interesting intermediates. The anaerobic gut bacterium Eubacterium ramulus can catabolize flavonoids, but until now, the pathway has not been experimentally confirmed. In the present work, a chalcone isomerase (CHI) and an enoate reductase (ERED) could be identified through whole genome sequencing and gene motif search. These two enzymes were successfully cloned and expressed in Escherichia coli in their active form, even under aerobic conditions. The catabolic pathway of E. ramulus was confirmed by biotransformations of flavanones into dihydrochalcones. The engineered E. coli strain that expresses both enzymes was used for the conversion of several flavanones, underlining the applicability of this biocatalytic cascade reaction. 相似文献
117.
Systematic Comparison of Peptidic Proteasome Inhibitors Highlights the α‐Ketoamide Electrophile as an Auspicious Reversible Lead Motif 下载免费PDF全文
Martin L. Stein Haissi Cui Philipp Beck Christian Dubiella Constantin Voss Prof. Dr. Achim Krüger Prof. Dr. Boris Schmidt Prof. Dr. Michael Groll 《Angewandte Chemie (International ed. in English)》2014,53(6):1679-1683
The ubiquitin–proteasome system (UPS) has been successfully targeted by both academia and the pharmaceutical industry for oncological and immunological applications. Typical proteasome inhibitors are based on a peptidic backbone endowed with an electrophilic C‐terminus by which they react with the active proteolytic sites. Although the peptide moiety has attracted much attention in terms of subunit selectivity, the target specificity and biological stability of the compounds are largely determined by the reactive warheads. In this study, we have carried out a systematic investigation of described electrophiles by a combination of in vitro, in vivo, and structural methods in order to disclose the implications of altered functionality and chemical reactivity. Thereby, we were able to introduce and characterize the class of α‐ketoamides as the most potent reversible inhibitors with possible applications for the therapy of solid tumors as well as autoimmune disorders. 相似文献
118.
Asymmetric Cascade Reaction to Allylic Sulfonamides from Allylic Alcohols by Palladium(II)/Base‐Catalyzed Rearrangement of Allylic Carbamates 下载免费PDF全文
Dipl.‐Chem. Johannes Moritz Bauer Dr. Wolfgang Frey Prof. Dr. René Peters 《Angewandte Chemie (International ed. in English)》2014,53(29):7634-7638
A regio‐ and enantioselective tandem reaction is reported capable of directly transforming readily accessible achiral allylic alcohols into chiral sulfonyl‐protected allylic amines. The reaction is catalyzed by the cooperative action of a chiral ferrocene palladacycle and a tertiary amine base and combines high step‐economy with operational simplicity (e.g. no need for inert‐gas atmosphere or catalyst activation). Mechanistic studies support a PdII‐catalyzed [3,3] rearrangement of allylic carbamates—generated in situ from the allylic alcohol and an isocyanate—as the key step, which is followed by a decarboxylation. 相似文献
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120.
David Rombach Hans‐Achim Wagenknecht 《Angewandte Chemie (International ed. in English)》2020,59(1):300-303
SF6 was applied as pentafluorosulfanylation reagent to prepare ethers with a vicinal SF5 substituent through a one‐step method involving photoredox catalysis. This method shows a broad substrate scope with respect to applicable alcohols for the conversion of α‐methyl and α‐phenyl styrenes. The products bear a new structural motif with two functional groups installed in one step. The alkoxy group allows elimination and azidation as further transformations into valuable pentafluorosulfanylated compounds. These results confirm that non‐toxic SF6 is a useful SF5 transfer reagent if properly activated by photoredox catalysis, and toxic reagents are completely avoided. In combination with light as an energy source, a high level of sustainability is achieved. Through this method, the proposed potential of the SF5 substituent in medicinal chemistry, agrochemistry, and materials chemistry may be exploited in the future. 相似文献