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31.
Pollock N Fowler G Twyman LJ McArthur SL 《Chemical communications (Cambridge, England)》2007,(24):2482-2484
This communication describes the synthesis and characterization of immobilized PAMAM dendrons onto a surface modified silicon wafer substrate (functionalized using plasma polymerized PAA) using a "growing from" strategy. 相似文献
32.
A short and convenient synthesis of 3-p-toluoyl-2-[4′-(3-diethylaminopropoxy)-phenyl]-benzofuran, an inhibitor of the aggregation of β-amyloid, which is thought to be the underlying cause of Alzheimer's disease, is described. 相似文献
33.
Being able to bind, select, and transport species is central to a number of fields, including medicine, materials, and environmental science. In particular, recognizing a specific species from one phase and transporting it across, or into another phase, has obvious applications in environ-mental science, for example, removal of unwanted or toxic materials from an aqueous or organic phase. In this paper, we describe an approach that uses a functionalized dendritic polymer to bind and transport a small anionic molecule across an organic phase (and between two aqueous phases). The design was based on encapsulation principles borrowed from nature, where anions are bound and transported by proteins that have specific sites within their globular ordered structures. For the work reported here, a globular dendritic polymer functionalized with an isophthalamide-based receptor was used to replace the protein structure and anion-binding site. Along with control experiments, the binding and transport properties of two functionalized HBPs were assessed using a Pressman U tube experiment. Both HBPs demonstrated an enhanced ability to bind and transport anions (when compared to the anion-binding site used in isolation). Furthermore, optimum binding and transport occurred when the smaller of the two HBPs were used. This supports our previous observations regarding the existence of a dense packed limit for HBPs. 相似文献
34.
35.
Thomas R. Koballa Jr Michael J. Dias Jennifer Lance Atkinson 《School science and mathematics》2009,109(7):403-414
Inquiry‐focused professional development and conceptions of inquiry held by eight professional development leaders were investigated within the context of a state science teacher conference. The prominent session format involved session leaders modeling classroom experiences. In all sessions, classroom inquiry was portrayed as a teacher‐guided activity with the primary goal being to increase motivation for engaging students in classroom inquiry. The leaders’ conceptualized inquiry primarily as a teaching approach with various goals, characteristics, and potential barriers. The findings of this study provide evidence of how inquiry, a prominent feature of science education reform, was portrayed in sessions at a conference sponsored by a state affiliate of the National Science Teachers Association and thought about by persons who led these sessions. The findings have implications for teacher learning from conference‐based professional development and its potential influence on science teacher thinking and practice. 相似文献
36.
Percec V Aqad E Peterca M Rudick JG Lemon L Ronda JC De BB Heiney PA Meijer EW 《Journal of the American Chemical Society》2006,128(50):16365-16372
Structural and retrostructural analysis of helical dendronized polyacetylenes (i.e., self-organizable polyacetylenes containing first generation dendrons or minidendrons as side groups) synthesized by the polymerization of minidendritic acetylenes with [Rh(nbd)Cl]2 (nbd = 2,5-norbornadiene) reveals an approximately 10% change in the average column stratum thickness (l) of the cylindrical macromolecules with a chiral periphery, through which a strong preference for a single-handed screw-sense is communicated. The cylindrical macromolecules reversibly interconvert between a three-dimensional (3D) centered rectangular lattice (Phi r-c,k) exhibiting long-range intracolumnar helical order at lower temperatures and a two-dimensional (2D) hexagonal columnar lattice (Phi h) with short-range helical order at higher temperatures. A polymer containing chiral, nonracemic peripheral alkyl tails is found to have a larger l as compared to the achiral polymers. In methyl cyclohexane solution, the same polymer exhibits an intense signal in circular dichroism (CD) spectra, whose intensity decreases upon heating. The observed change in l indicates that the chiral tails alter the polymer conformation from that of the corresponding polymer with achiral side chains. This change in conformation results in a relatively large free energy difference (DeltaGh) favoring one helix-sense over the other (per monomer residue). The capacity to distort the polymer conformation and corresponding free energy is related to the population of branches in the chiral tails and their distance from the polymer backbone by comparison to recently reported first and second generation dendronized polyphenylacetylenes. 相似文献
37.
We consider compact astrophysical objects formed from dark matter fermions of mass 250 GeV to 100 TeV or from massless fermions hidden by vacuum structure of similar energy scale. These objects have maximum stable masses of sub-planetary scale and radii of micron to centimeter scale. We describe the surface gravity and tidal forces near these compact ultra dense objects, as pertinent to signatures of their collisions with visible matter objects. 相似文献
38.
Chia-Lung Tsai Yow-Jon Lin Jia-Hong Chen Hsing-Cheng Chang Ya-Hui Chen Lance Horng Yu-Tai Shih 《Solid State Communications》2012,152(6):488-492
Zn0.8Co0.2O and Zn0.8Mn0.2O films were deposited on substrates by a sol–gel technique. X-ray diffraction, field-emission scanning electron microscopy, photoluminescence, and ferromagnetism measurements were used to characterize these dilute magnetic semiconductors. It is shown that the ferromagnetic properties might be related to the formation of acceptor-like defects in the Zn0.8Co0.2O and Zn0.8Mn0.2O films. It is found that ferromagnetic Zn0.8Mn0.2O has a higher Curie temperature than Zn0.8Co0.2O. In addition, the higher ratio of grain-boundary area to grain volume of Zn0.8Mn0.2O than Zn0.8Co0.2O indicates that grain boundaries and related acceptors are the intrinsic origin for ferromagnetism. 相似文献
39.
Dr. Anirban Bardhan Dr. Wes Brown Savannah Albright Prof. Michael Tsang Prof. Lance A. Davidson Prof. Alexander Deiters 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(17):e202318773
Conditionally controlled antisense oligonucleotides provide precise interrogation of gene function at different developmental stages in animal models. Only one example of small molecule-induced activation of antisense function exist. This has been restricted to cyclic caged morpholinos that, based on sequence, can have significant background activity in the absence of the trigger. Here, we provide a new approach using azido-caged nucleobases that are site-specifically introduced into antisense morpholinos. The caging group design is a simple azidomethylene (Azm) group that, despite its very small size, efficiently blocks Watson–Crick base pairing in a programmable fashion. Furthermore, it undergoes facile decaging via Staudinger reduction when exposed to a small molecule phosphine, generating the native antisense oligonucleotide under conditions compatible with biological environments. We demonstrated small molecule-induced gene knockdown in mammalian cells, zebrafish embryos, and frog embryos. We validated the general applicability of this approach by targeting three different genes. 相似文献
40.
Lance Horng G. Chern M. C. Chen P. C. Kang D. S. Lee 《Journal of magnetism and magnetic materials》2004,270(3):389-396
Epitaxial thin films of Fe3O4 and CoFe2O4 on MgO (0 0 1) substrates were grown by molecular beam epitaxy at low temperature growth process. Magnetization and hysteresis loop of both films were measured to investigate magnetic anisotropic properties at various temperatures. Anomalous magnetic properties are found to be correlated with crystalline, shape, and stress anisotropies. The Fe3O4 film below Verwey structural transition has a change in crystal structure, thus causing many anomalous magnetic properties. Crystalline anisotropy and anomalous magnetic properties are affected substantially by Co ions. The saturation magnetization of Co–ferrite film becomes much lower than that of Fe3O4 film, being very different from the bulks. It indicates that the low temperature growth process could not provide enough energy to have the lowest energy state. 相似文献