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91.
A new method for the simultaneous study of electrical and thermal properties of polymers is proposed. The thermal electrical analysis (TEA) combines the existing techniques of DSC (or DTA) with the electrical method of thermally stimulated discharge (TSD). TEA measurements were carried out with copolymers of methyl methacrylate (PMMA). The molecular origin of the TSD-current at the lower temperature side of the α1-relaxation process (glass transition Tg of the PMMA) is related to the disorientation of small polar segments of the comonomer (α2-relaxation) in the main chain of the PMMA. It can be shown that the TSD-current of the α2-relaxation (T > 80°C) increases with increasing comonomer content. This supports the molecular interpretation of the α2-process which is not reflected in the DSC. At higher temperatures frozen in dipoles regain their mobility and show a TSD peak at that temperature which corresponds to the Tg of the PMMA. The TSD ρ-peak at T>Tg can be attributed to trapped space charges which regain their freedom of motion. The results demonstrate the high resolution and resolving power of the TEA-method. TEA is recommended as an analyzing tool to investigate the relationship between the depolarization of dipoles, carrier transport, trapping of real charges and thermal transitions of polymers. 相似文献
92.
Dr. Andrea C. Kneuttinger Martin Winter Nadja A. Simeth Kristina Heyn Prof. Dr. Rainer Merkl Prof. Dr. Burkhard König Prof. Dr. Reinhard Sterner 《Chembiochem : a European journal of chemical biology》2018,19(16):1750-1757
The artificial regulation of proteins by light is an emerging subdiscipline of synthetic biology. Here, we used this concept to photocontrol both catalysis and allostery within the heterodimeric enzyme complex imidazole glycerol phosphate synthase (ImGP‐S). ImGP‐S consists of the cyclase subunit HisF and the glutaminase subunit HisH, which is allosterically stimulated by substrate binding to HisF. We show that a light‐sensitive diarylethene (1,2‐dithienylethene, DTE)‐based competitive inhibitor in its ring‐open state binds with low micromolar affinity to the cyclase subunit and displaces its substrate from the active site. As a consequence, catalysis by HisF and allosteric stimulation of HisH are impaired. Following UV‐light irradiation, the DTE ligand adopts its ring‐closed state and loses affinity for HisF, restoring activity and allostery. Our approach allows for the switching of ImGP‐S activity and allostery during catalysis and appears to be generally applicable for the light regulation of other multienzyme complexes. 相似文献
93.
Progressive Compression of 3D Mesh Geometry Using Sparse Approximations from Redundant Frame Dictionaries 下载免费PDF全文
In this paper, we present a new approach for the progressive compression of three‐dimensional (3D) mesh geometry using redundant frame dictionaries and sparse approximation techniques. We construct the proposed frames from redundant linear combinations of the eigenvectors of a combinatorial mesh Laplacian matrix. We achieve a sparse synthesis of the mesh geometry by selecting atoms from a frame using matching pursuit. Experimental results show that the resulting rate‐distortion performance compares favorably with other progressive mesh compression algorithms in the same category, even when a very simple, sub‐optimal encoding strategy is used for the transmitted data. The proposed frames also have the desirable property of being able to be applied directly to a manifold mesh having arbitrary topology and connectivity types; thus, no initial remeshing is required and the original mesh connectivity is preserved. 相似文献
94.
Starch was isolated from fermented sorghum flour (24 h natural lactic acid fermentation), and water retention, starch solubility, clarity of starch pastes and freeze‐thaw stability were measured. In comparison with starch isolated from unfermented sorghum flour, fermentation increased the solubility of the starch and decreased the water retention, but it had no effect on the freeze‐thaw stability of the starch. There was no substantial difference in the starch paste clarity between the two samples. Storage of starch pastes at lower temperature (4°C) resulted in a very low clarity of starch. 相似文献
95.
Maria T. Lblein Isabel Falke Hans Theodor Eich Burkhard Greve Martin Gtte Fabian M. Troschel 《International journal of molecular sciences》2021,22(21)
In ovarian cancer, therapy resistance mechanisms complicate cancer cell eradication. Targeting Musashi RNA-binding proteins (MSI) may increase therapeutic efficacy. Database analyses were performed to identify gene expression associations between MSI proteins and key therapy resistance and cancer stem cell (CSC) genes. Then, ovarian cancer cells were subjected to siRNA-based dual knockdown of MSI-1 and MSI-2. CSC and cell cycle gene expression was investigated using quantitative polymerase chain reaction (qPCR), western blots, and flow cytometry. Metabolic activity and chemoresistance were assessed by MTT assay. Clonogenic assays were used to quantify cell survival post-irradiation. Database analyses demonstrated positive associations between MSI proteins and putative CSC markers NOTCH, MYC, and ALDH4A1 and negative associations with NOTCH inhibitor NUMB. MSI-2 expression was negatively associated with the apoptosis regulator p21. MSI-1 and MSI-2 were positively correlated, informing subsequent dual knockdown experiments. After MSI silencing, CSC genes were downregulated, while cell cycle progression was reduced. Metabolic activity was decreased in some cancer cells. Both chemo- and radioresistance were reduced after dual knockdown, suggesting therapeutic potential. Dual knockdown of MSI proteins is a promising venue to impede tumor growth and sensitize ovarian cancer cells to irradiation and chemotherapy. 相似文献
96.
M. Bram C. Stiller H. P. Buchkremer D. Stver H. Baur 《Advanced Engineering Materials》2000,2(4):196-199
The production of highly porous parts from titanium, stainless steel, and nickel‐based superalloys is of increasing interest in lightweight constructions. A new space‐holder method uses carbamide (urea) and ammonium hydrogen carbonate to produce samples with porosities between 60 and 80 %. Depending on the shape and size distribution of the space holder, spherical and angular pores in the range of 0.1–2.5 mm were obtained. 相似文献
97.
Dietrich Braun Burkhard Schmiedel Gtz P. Hellmann Morand Lambla Michael Schneider 《大分子材料与工程》1998,254(1):79-84
Natural latex (NR) particles, modified with a hard shell of poly(methyl methacrylate) (PMMA) and with a substructure of PMMA (type "NR-M") or polystyrene (type "NR-SM"), were tested as compatibilizers in blends of polycarbonate (of bisphenol A, PC) and PMMA or PS. During melt blending, the modified NR particles were torn apart, from an original size of >0.5 μm down to ≅0.1 μm in diameter. Two different types of particle distribution were observed in the blends: in PC/PMMA/NR-M blends, the NR-M particles were dispersed in the PMMA phase, whereas, in PC/PS/NR-SM blends, the NR-SM particles formed interface layers between PC and PS phase domains. The latter blend morphology, distinguished by continuous rubbery interface layers of NR-SM, turned out to be mechanically excellent in injection-moulded parts. The poor impact strength of PC/PS was raised by an order of magnitude. The effect depends on the orientation in the injection-moulded test bars. 相似文献
98.
99.
Dayon L Hainard A Licker V Turck N Kuhn K Hochstrasser DF Burkhard PR Sanchez JC 《Analytical chemistry》2008,80(8):2921-2931
A new 6-plex isobaric mass tagging technology is presented, and proof of principle studies are carried out using standard protein mixtures and human cerebrospinal fluid (CSF) samples. The Tandem Mass Tags (TMT) comprise a set of structurally identical tags which label peptides on free amino-terminus and epsilon-amino functions of lysine residues. During MS/MS fragmentation, quantification information is obtained through the losses of the reporter ions. After evaluation of the relative quantification with the 6-plex version of the TMT on a model protein mixture at various concentrations, the quantification of proteins in CSF samples was performed using shotgun methods. Human postmortem (PM) CSF was taken as a model of massive brain injury and comparison was carried out with antemortem (AM) CSF. After immunoaffinity depletion, triplicates of AM and PM CSF pooled samples were reduced, alkylated, digested by trypsin, and labeled, respectively, with the six isobaric variants of the TMT (with reporter ions from m/z = 126.1 to 131.1 Th). The samples were pooled and fractionated by SCX chromatography. After RP-LC separation, peptides were identified and quantified by MS/MS analysis with MALDI TOF/TOF and ESI-Q-TOF. The concentration of 78 identified proteins was shown to be clearly increased in PM CSF samples compared to AM. Some of these proteins, like GFAP, protein S100B, and PARK7, have been previously described as brain damage biomarkers, supporting the PM CSF as a valid model of brain insult. ELISA for these proteins confirmed their elevated concentration in PM CSF. This work demonstrates the validity and robustness of the tandem mass tag (TMT) approach for quantitative MS-based proteomics. 相似文献
100.
Manfred Lamprecht Simon Bogner Gert Schippinger Kurt Steinbauer Florian Fankhauser Seth Hallstroem Burkhard Schuetz Joachim F Greilberger 《Journal of the International Society of Sports Nutrition》2012,9(1):1-13