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181.
We investigate a wetting reversal transition in thin films of two-phase mixtures of poly(ethylene-propylene) (PEP) and its deuterated analogue (dPEP) on a substrate covered by a self-assembled monolayer (SAM) whose surface energy, γSAM, is tuned by varying the SAM composition. As γSAM increases from 21 to 24 mJ/m2, a transition from a three-layer (air/dPEP/PEP/dPEP/SAM) to a two-layer (air/dPEP/PEP/SAM) structure occurs at increasing Tc - T, where Tc and T are the critical and transition temperatures, respectively. As the system structure changes from three-layer to two-layer, the thicknesses of the dPEP-rich wetting layers at the air/mixture and mixture/SAM interfaces are found to smoothly increase and decrease, respectively, while the thickness of the PEP-rich layer (ca. one half of the total film thickness) does not change. The dependence of the transition temperature on γSAM is predicted by a simple model using the experimental data on the surface energies of PEP/dPEP and estimates of the interfacial energy between PEP and dPEP. 相似文献
182.
Brian B. Frank Berta Camafort Blanco Samuel Jakob Fiammetta Ferroni Silvia Pieraccini Dr. Alberta Ferrarini Prof. Dr. Corinne Boudon Prof. Dr. Jean‐Paul Gisselbrecht Dr. Paul Seiler Gian Piero Spada Prof. Dr. François Diederich Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(36):9005-9016
Axially chiral, N‐arylated 3,5‐dihydro‐4H‐dinaphtho[2,1‐c:1′,2′‐e]azepines have been prepared by short synthetic protocols from enantiopure 1,1′‐bi(2,2′‐naphthol) (BINOL) and anilines. Alkynes substituted with two N‐phenyldinaphthazepine donors readily undergo a formal [2+2] cycloaddition, followed by retro‐electrocyclization, with tetracyanoethene (TCNE) to yield donor‐substituted 1,1,4,4‐tetracyanobuta‐1,3‐dienes (TCBDs) featuring intense intramolecular charge‐transfer (CT) interactions. A dicyanovinyl derivative substituted with one N‐phenyldinaphthazepine donor was obtained by a “one‐pot” oxidation/Knoevenagel condensation from the corresponding propargylic alcohol. Comparative electrochemical, X‐ray crystallographic, and UV/Vis studies show that the electron‐donor qualities of N‐phenyldinaphthazepine are similar to those of N,N‐dimethylanilino residues. The circular dichroism (CD) spectrum of a push–pull chromophore incorporating the chiral donor moiety features Cotton effects of exceptional intensity. With their elongated shape and the rigidity of the chiral N‐aryldinaphthazepine donors, these chromophores are effective inducers of twist distortion in nematic liquid crystals (LCs). Thus, a series of the dinaphthazepine derivatives was used as dopants in the nematic LC E7 (Merck) and high helical twisting powers (β) of the order of hundreds of μm?1 were measured. Theoretical calculations were employed to elucidate the relation between the structure of the dopants and their helical twisting power. For the derivatives with two dinaphthazepine moieties, a strong dependence of the β‐values on the structure and conformation of the linker between them was found. 相似文献
183.
Roland Jakob‐Roetne Helmut Jacobsen 《Angewandte Chemie (International ed. in English)》2009,48(17):3030-3059
Mind how you go : The current strategies for the development of therapies for Alzheimer's disease are very diverse. Particular attention is given to the search for inhibitors (see picture for two examples) of the proteolytic enzyme β‐ and γ‐secretase, which inhibits the cleavage of the amyloid precursor proteins into amyloid β peptides, from which the disease‐defining deposits of plaque in the brains of Alzheimer's patients originates.
184.
Lateral flow (immuno)assay: its strengths,weaknesses, opportunities and threats. A literature survey 总被引:2,自引:0,他引:2
Posthuma-Trumpie GA Korf J van Amerongen A 《Analytical and bioanalytical chemistry》2009,393(2):569-582
Lateral flow (immuno)assays are currently used for qualitative, semiquantitative and to some extent quantitative monitoring
in resource-poor or non-laboratory environments. Applications include tests on pathogens, drugs, hormones and metabolites
in biomedical, phytosanitary, veterinary, feed/food and environmental settings. We describe principles of current formats,
applications, limitations and perspectives for quantitative monitoring. We illustrate the potentials and limitations of analysis
with lateral flow (immuno)assays using a literature survey and a SWOT analysis (acronym for “strengths, weaknesses, opportunities,
threats”). Articles referred to in this survey were searched for on MEDLINE, Scopus and in references of reviewed papers.
Search terms included “immunochromatography”, “sol particle immunoassay”, “lateral flow immunoassay” and “dipstick assay”. 相似文献
185.
Jakob Jonsson 《Journal of Algebraic Combinatorics》2009,29(1):81-90
J.L. Andersen proved that there is 5-torsion in the bottom nonvanishing homology group of the simplicial complex of graphs
of degree at most two on seven vertices. We use this result to demonstrate that there is 5-torsion also in the bottom nonvanishing
homology group of the matching complex
on 14 vertices. Combining our observation with results due to Bouc and to Shareshian and Wachs, we conclude that the case
n=14 is exceptional; for all other n, the torsion subgroup of the bottom nonvanishing homology group has exponent three or is zero. The possibility remains that
there is other torsion than 3-torsion in higher-degree homology groups of
when n≥13 and n≠14.
Research of J. Jonsson was supported by European Graduate Program “Combinatorics, Geometry, and Computation”, DFG-GRK 588/2. 相似文献
186.
Jakob Lemvig 《Advances in Computational Mathematics》2009,30(3):231-247
For sufficiently small translation parameters, we prove that any bandlimited function ψ, for which the dilations of its Fourier transform form a partition of unity, generates a wavelet frame with a dual frame
also having the wavelet structure. This dual frame is generated by a finite linear combination of dilations of ψ with explicitly given coefficients. The result allows a simple construction procedure for pairs of dual wavelet frames whose
generators have compact support in the Fourier domain and desired time localization. The construction is based on characterizing
equations for dual wavelet frames and relies on a technical condition. We exhibit a general class of function satisfying this
condition; in particular, we construct piecewise polynomial functions satisfying the condition.
相似文献
187.
Fristrup P Jensen T Hoppe J Norrby PO 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(20):5352-5360
An analysis of product distributions in the Tsuji-Trost reaction indicates that several instances of reported "memory effects" can be attributed to slow interconversion of the initially formed syn- and anti-[Pd(eta3-allyl)] complexes. Addition of chloride triggers a true memory effect, in which the allylic terminus originally bearing the leaving group has a higher reactivity. The latter effect, termed regioretention, can be rationalized by ionization from a palladium complex bearing a chloride ion, forming an unsymmetrically substituted [Pd(eta3-allyl)] complex. DFT calculations verify that the position trans to the phosphine ligand is more reactive both in the initial ionization and in the subsequent nucleophilic attack. 相似文献
188.
Irradiation of 2-(alkoxymethyl)-5-methyl-alpha-chloroacetophenones (1a-c) and 2-(methoxymethyl)-5-methylphenacyl benzoate (1d) in dry, nonnucleophilic solvents afforded 3-alkoxy-6-methylindan-1-ones (3a-c) in very high chemical yields. 3-Methylisobenzofuran-1(3H)-one (2) was, however, isolated as a major photoproduct in the presence of trace amounts of water. Quenching experiments and laser flash spectroscopy revealed that the indanone derivatives 3 are formed by 1,5-hydrogen migration from the lowest triplet excited state of the acetophenones 1 and cyclization of the resulting photoenols. In contrast, production of the lactone 2 in wet solvents was found to result from two consecutive photochemical transformations. The photoenols produced by photolysis of 1a-c add water as a nucleophile to form 2-acetyl-4-methylbenzaldehyde (4), which is further converted to 2 via a second, singlet state photoenolization process. Exhaustive photolysis of 1a in methanol produced the acetal 2-(dimethoxymethyl)-5-methylacetophenone (7a) as the exclusive product. The remarkable selectivity of these photoreactions may well be useful in synthetic organic chemistry. 相似文献
189.
190.
Plasma treatments are established methods to functionalise carbon nanotubes (CNTs) and modify their surface structure. This paper presents a mild glow‐discharge plasma treatment of aligned arrays of multi‐walled carbon nanotubes employing sulfur hexafluoride (SF6), ammonia (NH3), and their mixtures as process gases. For the latter, sulfur was detected at the tip and sidewalls of the nanotubes via energy‐dispersive X‐ray spectroscopy, while electron microscopy served as method to verify the structural integrity of the CNTs after the plasma treatment. This approach provides the basis for an easy and quick alternative to existing sulfur functionalisation methods of MWCNTs. Furthermore, the proposed method can conveniently be applied to carbon nanotube arrays on substrate while preserving their structure and alignment.