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排序方式: 共有153条查询结果,搜索用时 15 毫秒
61.
Tuomas Aitasalo Jukka Hassinen Jorma Holsa Taneli Laamanen Mika Lastusaari Marja Malkamaki Janne Niittykoski Pavel Novak 《中国稀土学报(英文版)》2009,27(4):529-538
The electronic and defect energy level structure of polycrystalline Sr2MgSi2O7:Eu2+,R3+ persistent luminescence materials were studied with thermoluminescence and different synchrotron radiation spectroscopies (UV-VUV emission and excitation, X-ray absorption near-edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS)). Special attention was paid on the effect of the R3+ co-dopants on the persistent luminescence properties of the materials. Theoretical calculations using the density functional theory (DFT) were carried out simultaneously with the experimental work. The experimental band gap energy (Eg) value of ca. 7.1 eV agreed very well with the DFT value of 6.7 eV. The variation of the Eg value was attempted to relate with the trap structure as well as with the different properties of the R3+ co-dopants. The trap level energy distribution depended strongly on the R3+ co-dopant except for the shallowest trap energy above the room temperature remaining practically the same, however. The different processes in the mechanism of persistent luminescence from Sr2MgSi2O7:Eu2+,R3+ were assembled and their contributions discussed. 相似文献
62.
63.
Crosslinkable poly(lactic acid)‐based materials: Biomass‐derived solution for barrier coatings 下载免费PDF全文
The demand for biobased barrier packaging alternatives is constantly growing. Poly(lactic acid) (PLA)‐based polymers are one of the most extensively studied biomass‐derived synthetic polymers; however, they typically lack water‐barrier properties. We synthesized a copolymer of d ,l ‐lactic acid, 1,4‐butanediol, and itaconic acid [poly(d ,l ‐lactic acid–1,4‐butanediol–itaconic acid) (PLABDIA)] via bulk polycondensation. The radical crosslinking reactions of the synthesized polymer were investigated with bulk crosslinking trials to find a formulation that was suitable for a rapidly crosslinkable barrier coating. The crosslinking efficiency was tested with methacrylate and acrylate crosslinkers together with peroxide radical initiators. Poly(ethylene glycol) diacrylate (number‐average molecular weight = 250 g/mol) together with dilauroyl peroxide proved to be the best crosslinker–initiator combination. An aqueous dispersion of PLABDIA was prepared with a thermomechanical method and applied to commercial boxboard on a pilot‐scale line coater. With a coating weight of 10 g/m2, a water vapor transmission rate of 22.8 g/m2d was achieved, and this coating outperformed commercial extruded PLA coatings. The samples also showed very good grease resistance and would, therefore, be a good solution for the packaging of dry and fatty goods. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44326. 相似文献
64.
Prolonged Dye Release from Mesoporous Silica‐Based Imaging Probes Facilitates Long‐Term Optical Tracking of Cell Populations In Vivo 下载免费PDF全文
Jessica M. Rosenholm Tina Gulin‐Sarfraz Veronika Mamaeva Rasmus Niemi Ezgi Özliseli Diti Desai Daniel Antfolk Eva von Haartman Desiré Lindberg Neeraj Prabhakar Tuomas Näreoja Cecilia Sahlgren 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(12):1578-1592
Nanomedicine is gaining ground worldwide in therapy and diagnostics. Novel nanoscopic imaging probes serve as imaging tools for studying dynamic biological processes in vitro and in vivo. To allow detectability in the physiological environment, the nanostructure‐based probes need to be either inherently detectable by biomedical imaging techniques, or serve as carriers for existing imaging agents. In this study, the potential of mesoporous silica nanoparticles carrying commercially available fluorochromes as self‐regenerating cell labels for long‐term cellular tracking is investigated. The particle surface is organically modified for enhanced cellular uptake, the fluorescence intensity of labeled cells is followed over time both in vitro and in vivo. The particles are not exocytosed and particles which escaped cells due to cell injury or death are degraded and no labeling of nontargeted cell populations are observed. The labeling efficiency is significantly improved as compared to that of quantum dots of similar emission wavelength. Labeled human breast cancer cells are xenotransplanted in nude mice, and the fluorescent cells can be detected in vivo for a period of 1 month. Moreover, ex vivo analysis reveals fluorescently labeled metastatic colonies in lymph node and rib, highlighting the capability of the developed probes for tracking of metastasis. 相似文献
65.
Ayaka Kamada Aviad Levin Zenon Toprakcioglu Yi Shen Viviane Lutz‐Bueno Kevin N. Baumann Pezhman Mohammadi Markus B. Linder Raffaele Mezzenga Tuomas P. J. Knowles 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(9)
Protein‐based fibers are used by nature as high‐performance materials in a wide range of applications, including providing structural support, creating thermal insulation, and generating underwater adhesives. Such fibers are commonly generated through a hierarchical self‐assembly process, where the molecular building blocks are geometrically confined and aligned along the fiber axis to provide a high level of structural robustness. Here, this approach is mimicked by using a microfluidic spinning method to enable precise control over multiscale order during the assembly process of nanoscale protein nanofibrils into micro‐ and macroscale fibers. By varying the flow rates on chip, the degree of nanofibril alignment can be tuned, leading to an orientation index comparable to that of native silk. It is found that the Young's modulus of the resulting fibers increases with an increasing level of nanoscale alignment of the building blocks, suggesting that the mechanical properties of macroscopic fibers can be controlled through varying the level of ordering of the nanoscale building blocks. Capitalizing on strategies evolved by nature, the fabrication method allows for the controlled formation of macroscopic fibers and offers the potential to be applied for the generation of further novel bioinspired materials. 相似文献
66.
67.
Sajal Maity Madhuri Hande Tuomas Lönnberg 《Chembiochem : a European journal of chemical biology》2020,21(16):2321-2328
Oligonucleotides incorporating a central C-nucleoside with either a rigid or flexible benzaldoxime base moiety have been synthesized, and the hybridization properties of their metallacyclic derivatives have been studied by UV melting experiments. In all cases, the metallated duplexes were less stable than their unmetallated counterparts, and the metallacyclic nucleobases did not show a clear preference for any of the canonical nucleobases as a base-pairing partner. With palladated oligonucleotides, increased flexibility translated to less severe destabilization, whereas the opposite was true for the mercurated oligonucleotides; this reflects the greater difficulties in accommodating a rigid PdII-mediated base pair than a rigid HgII-mediated base pair within the base stack of a double helix. 相似文献
68.
J. Magnus Rahm Christopher Tiburski Tuomas P. Rossi Ferry Anggoro Ardy Nugroho Sara Nilsson Christoph Langhammer Paul Erhart 《Advanced functional materials》2020,30(35)
Accurate complex dielectric functions are critical to accelerate the development of rationally designed metal alloy systems for nanophotonic applications, and to thereby unlock the potential of alloying for tailoring nanostructure optical properties. To date, however, accurate alloy dielectric functions are widely lacking. Here, a time‐dependent density‐functional theory computational framework is employed to compute a comprehensive binary alloy dielectric function library for the late transition metals most commonly employed in plasmonics (Ag, Au, Cu, Pd, Pt). Excellent agreement is found between electrodynamic simulations based on these dielectric functions and selected alloy systems experimentally scrutinized in 10 at% composition intervals. Furthermore, it is demonstrated that the dielectric functions can vary in very non‐linear fashion with composition, which paves the way for non‐trivial optical response optimization by tailoring material composition. The presented dielectric function library is thus a key resource for the development of alloy nanomaterials for applications in nanophotonics, optical sensors, and photocatalysis. 相似文献
69.
Alexander Drobchenko Joni-Kristian Kamarainen Lasse Lensu Jarkko Vartiainen Heikki K?lvi?inen Tuomas Eerola 《Frontiers of Electrical and Electronic Engineering in China》2011,6(2):328-338
Fine and sparse details appear in many quality inspection applications requiring machine vision. Especially on flat surfaces,
such as paper or board, the details can be made detectable by oblique illumination. In this study, a general definition of
such details is given by defining sufficient statistical properties from histograms. The statistical model allows simulation
of data and comparison of methods designed for detail detection. Based on the definition, utilization of the existing thresholding
methods is shown to be well motivated. The comparison shows that minimum error thresholding outperforms the other standard
methods. Finally, the results are successfully applied to a paper printability inspection application, and the IGT picking
assessment, in which small surface defects must be detected. The provided method and measurement system prototype provide
automated assessment with results comparable to manual expert evaluations in this laborious task. 相似文献
70.
Dr. Tuomas A. Lönnberg 《Chembiochem : a European journal of chemical biology》2012,13(18):2690-2700
A 2′‐O‐methyl‐RNA oligonucleotide containing a single free 2′‐OH group flanking a branching phosphotriester linkage was prepared as a model for phosphate‐branched RNA by using an orthogonally protected dimeric phosphoramidite building block in solid‐phase synthesis. The strategy allows the synthesis of phosphate‐branched oligonucleotides, the three branches of which may be of any desired sequence. Hydrolytic reactions of the phosphotriester linkages in such oligonucleotides were studied at physiological pH in the presence (and absence) of various complementary oligonucleotides. The fully hybridized oligonucleotide model is an order of magnitude more stable than its single‐stranded counterpart, which, in turn, is an order of magnitude more stable than its trinucleoside phosphotriester core lacking any oligonucleotide arms. Furthermore, kinked structures obtained by hybridizing the phosphate‐branched oligonucleotide with partially complementary oligonucleotides are three to five times more stable than fully double‐stranded ones and only approximately three times less stable than the so‐called RNA X structure, which has been postulated to incorporate an RNA phosphotriester linkage. The results indicate that when the intrinsically unstable RNA phosphotriester linkage is embedded in an oligonucleotide of appropriate tertiary structure, its half‐life can be at least several hours. 相似文献