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581.
Leonid Yaroslavsky Chad Goerzen Stanislav Umansky H. John Caulfield 《Central European Journal of Physics》2010,8(3):455-462
Although optics-less cutaneous (“skin”) vision is not uncommon among living organisms, its mechanisms and capabilities have not been thoroughly investigated. This paper demonstrates, using methods from statistical parameter estimation theory and numerical simulations, that arrays of bare radiation detectors arranged on a planar or curved surface have the ability to perform imaging tasks without any optics at all. The working principle of this type of optics-less sensors and the model developed here for determining their performance may be used to shed light on possible mechanisms, capabilities and evolution of cutaneous vision in nature. 相似文献
582.
Chad M. Higa Andy T. Tek Rudy J. Wojtecki Rebecca Braslau 《Journal of polymer science. Part A, Polymer chemistry》2018,56(21):2397-2411
Branched and linear nonmigratory internal plasticizers attached to PVC by a pendant triazole linkage were synthesized and investigated. Copper-free azide-alkyne thermal cycloaddition was employed to covalently bind triazole-based phthalate mimics to PVC. To systematically investigate the effect of plasticizer structure on glass transition temperature, several architectural motifs were explored. Free volume theory was considered when designing many of these internal plasticizers: hexyl-tethers were utilized to generate additional space between the triazole-phthalate mimic and the polymer backbone. Miscibility of these triazole-plasticizers in PVC is important: variation of the ester moieties on the triazole possessing alkyl and/or poly(ethylene oxide) chains produced a wide range of glass transition temperatures (Tg): from anti-plasticizing 96 °C, to highly efficient plasticized materials exhibiting Tg values as low as −42 °C. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2397–2411 相似文献
583.
The design and synthesis of a new class of gold nanoparticle with guanosine monophosphate derivatives or G-rich oligonucleotides as their surface ligands are described. These nanoparticles spontaneously form macroscopic assemblies at low temperature and relatively high salt concentrations, which is attributed to the cooperative formation of guanosine quartets and G-quadruplexes between the individual nanoparticles. Significantly, the solution behavior of these nanoparticles is highly controllable by adjusting solution parameters (including temperature, ionic strength, and ion species) and the sequence of the G-rich oligonucleotide 相似文献
584.
Barlow S Risko C Chung SJ Tucker NM Coropceanu V Jones SC Levi Z Brédas JL Marder SR 《Journal of the American Chemical Society》2005,127(48):16900-16911
(E)-4,4'-Bis[bis(4-methoxyphenyl)amino]stilbene, 1, (E,E)-1,4-bis[4-[bis(4-methoxyphenyl)amino]styryl]benzene, 2, and two longer homologues, (E,E,E)-4,4'-bis[4-[bis(4-methoxyphenyl)amino]styryl]stilbene, 3, and (E,E,E,E)-1,4-bis(4-[4-[bis(4-methoxyphenyl)amino]styryl]styryl)benzene, 4, have been oxidized to their mono- and dications using tris(4-bromophenyl)aminium hexachloroantimonate. The intervalence charge-transfer (IVCT) band of 1(+) is narrow and asymmetric and exhibits only weak solvatochromism. Analysis of this band indicates that 1(+) is a class-III or class-II/III borderline mixed-valence species. In contrast, a broad, strongly solvatochromic IVCT band is observed for 2(+), indicating that this species is a class-II mixed-valence species. The assignment of 1(+ ) and 2(+) as symmetric class-III and unsymmetric class-II species, respectively, is also supported by AM1 calculations. Hush analysis of the IVCT bands of both 1(+) and 2(+) gives larger electronic couplings, V, than for their analogues in which the double bonds are replaced with triple bonds. The diabatic electron-transfer distance, R, in 1(+) can be estimated by comparison of the V estimated by Hush analysis and from the IVCT maximum; it is considerably less than the geometric N-N separation, a result supported by quantum-chemical estimates of R for 1(+)-4(+). In 3(+) and 4(+), the IVCT is largely obscured by an intense absorption similar to a band seen in the corresponding dications and to that observed in the monocation of a model compound, (E,E,E)-1-[bis(4-methoxyphenyl)amino]-4-[4-[4-(4-tert-butylstyryl)styryl]styryl]benzene, 5, containing only one nitrogen redox center; we attribute this band to a bridge-to-N(+) transition. The corresponding dications 1(2+)-4(2+) show a complementary trend in the coupling between redox centers: the shortest species is diamagnetic, while the dication with the longest bridge behaves as two essentially noninteracting radical centers. 相似文献
585.
Three-layer composite magnetic nanoparticle probes for DNA 总被引:3,自引:0,他引:3
A method for synthesizing composite nanoparticles with a gold shell, an Fe3O4 inner shell, and a silica core has been developed. The approach utilizes positively charged amino-modified SiO2 particles as templates for the assembly of negatively charged 15 nm superparamagnetic water-soluble Fe3O4 nanoparticles. The SiO2-Fe3O4 particles electrostatically attract 1-3 nm Au nanoparticle seeds that act in a subsequent step as nucleation sites for the formation of a continuous gold shell around the SiO2-Fe3O4 particles upon HAuCl4 reduction. The three-layer magnetic nanoparticles, when functionalized with oligonucleotides, exhibit the surface chemistry, optical properties, and cooperative DNA binding properties of gold nanoparticle probes, but the magnetic properties of the Fe3O4 inner shell. 相似文献
586.
C. Chad Roberts Tom M. Apple Gary E. Wnek 《Journal of polymer science. Part A, Polymer chemistry》2000,38(19):3486-3497
4‐(Phenylethynyl‐α,β‐13C)phthalic anhydride (PEPA) and 13C‐labeled phenylethynyl‐terminated imide (PETI) oligomers were synthesized, and solid‐state 13C nuclear magnetic resonance (NMR) spectroscopy was used to determine the structure of cured oligomers. Solid‐state 13C NMR spectra were collected before and after thermal curing. Using solid‐state 13C NMR difference spectroscopy, several cure products were identified. The observed 13C NMR resonances were assigned to four different classes of cure products: aromatics, products from backbone addition (substituted stilbenes and tetraphenylethanes), polyenes, and cyclobutadiene cyclodimers. The effects of postcuring and oligomer chain length on the structure of the cured resins were examined. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3486–3497, 2000 相似文献
587.
A theory is presented for the flow-induced fiber orientation and stress in fiber-reinforced polymer composites with planar fiber orientation. The rate of change of fiber orientation is given as a function of the strain rate in the continuum and the probabilistic effects of physical inter-fiber contacts. The continuum stress is calculated from the stress in the fluid and fibers, where fiber stress is a result of the local disturbance in the fluid velocity field and of the inter-fiber contact forces. Fiber orientation is described via a probability density function whose transport equation has the form of a standard advection-diffusion equation with an orientation-dependent rotary diffusion. This equation is solved using a finite difference scheme and the results are presented. 相似文献