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1.
2.
Corwin Hansch Friederike Helmer 《Journal of polymer science. Part A, Polymer chemistry》1968,6(12):3295-3302
By using substituent constants and regression analysis, an analysis has been made of the binding of derivatives of aniline and acetanilide to nylon and rayon, the experimental data of Ward and Upchurch being used. The amount of organic compounds bound from an aqueous solution by these two types of synthetic macromolecules is shown to be related to the octanol–water partition coefficients P. In the case of the aniline derivatives, where the basicity of the compounds varied considerably, a good model describing binding results from the linear combination of the two parameters related to free energy, i.e., log P and ΔpKa. The latter term is the difference between pKa for aniline and a particular derivative. For the neutral acetanilides a simple linear free-energy relation between log P and log K is found. Of special note is the fact that the dependence of binding of these two classes of compounds to two classes of synthetic macromolecules as indicated by the coefficient with the log P term very closely parallels that found for a variety of biopolymers. The mechanism of hydrophobic binding seems to be the same in both the synthetic and natural polymers. 相似文献
3.
C. Ratsch C. Anderson R. E. Caflisch L. Feigenbaum D. Shaevitz M. Sheffler C. Tiee 《Applied Mathematics Letters》2003,16(8):1165-1170
We adapt the level-set method to simulate epitaxial growth of thin films on a surface that consists of different reconstruction domains. Both the island boundaries and the boundaries of the reconstruction domains are described by different level-set functions. A formalism of coupled level-set functions that describe entirely different physical properties is introduced, where the velocity of each level-set function is determined by the value of the other level-set functions. 相似文献
4.
D. Thao Nguyen Matthias Freitag Christian Gutheil Dr. Kai Sotthewes Dr. Bonnie J. Tyler Dr. Marcus Böckmann Mowpriya Das Friederike Schlüter Prof. Dr. Nikos L. Doltsinis Prof. Dr. Heinrich F. Arlinghaus Prof. Dr. Bart Jan Ravoo Prof. Dr. Frank Glorius 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(32):13754-13759
5.
For pairing based cryptography we need elliptic curves defined over finite fields
whose group order is divisible by some prime
with
where k is relatively small. In Barreto et al. and Dupont et al. [Proceedings of the Third Workshop on Security in Communication Networks (SCN 2002), LNCS, 2576, 2003; Building curves with arbitrary small Mov degree over finite fields, Preprint, 2002], algorithms for the construction of ordinary elliptic curves over prime fields
with arbitrary embedding degree k are given. Unfortunately, p is of size
.We give a method to generate ordinary elliptic curves over prime fields with p significantly less than
which also works for arbitrary k. For a fixed embedding degree k, the new algorithm yields curves with
where
or
depending on k. For special values of k even better results are obtained.We present several examples. In particular, we found some curves where
is a prime of small Hamming weight resp. with a small addition chain.AMS classification: 14H52, 14G50 相似文献
6.
Jester SS Idelson A Schmitz D Eberhagen F Höger S 《Langmuir : the ACS journal of surfaces and colloids》2011,27(13):8205-8215
Shape-persistent rigid phenylene-ethynylene-butadiynylenes form lamellar self-assembled monolayers (SAMs) at the HOPG/TCB interface, which were studied by scanning tunneling microscopy (STM) with submolecular resolution. Substitution of the terminating acetylene functions with polar cyanopropyldimethylsilyl groups leads to 2D phase separation and defined rod-rod interactions, which determine the packing distances between the rigid rods. The results stimulated the connection of rigid rods via septiarylene clamp units. They covalently link two rigid rod units and define the intramolecular rod-rod distance that matches the alkoxy substituent chain lengths. The systems can be described as half-ring structures of two rigid rods connected via a rotatable joint unit. These acetylene-terminated half-ring structures were also oligomerized under Cu and Pd catalysis to yield defined acyclic and cyclic oligomers. Detailed STM studies decoded the molecular origin of the surface patterning of such systems. The dodecyloxy side chains are adsorbed along the HOPG main axes and, together with the alkoxy backbone angle, determine the adsorption direction of the adlayers. 相似文献
7.
Laser-induced breakdown spectroscopy has been used for quantitative measurement of trace elements, e.g. sulfur and chlorine,
in concrete. Chloride and sulfate ions have a large effect on the durability of concrete structures, and quantitative measurement
is important for condition assessment and quality assurance. Concrete is a highly heterogeneous material in composition and
grain-size distribution, i.e. the spatial distribution of elements. Calibration plots were determined by use of laboratory-made
reference samples consisting of pressings of cement powder, hydrated cement, cement mortar, and concrete, in which the heterogeneity
of the material is increasing because of the aggregates. Coarse aggregate and cement paste are distinguishable by the intensity
of the Ca spectral lines. More advanced evaluation is necessary to account for the effect of the fine aggregate. The three
series of reference samples enable systematic study of the effects of heterogeneity on spectral intensity, signal fluctuation,
uncertainty, and limits of detection. Spatially resolved measurements and many spectra enable statistical evaluation of the
data. The heterogeneity has an effect on measurement of the sulfur and chlorine content, because both occur mainly in the
cement matrix. Critical chloride concentrations are approximately 0.04% (m/m). The chlorine spectral line at 837.6 nm is evaluated. The natural sulfur content of concrete is approximately 0.1% (m/m). The spectral line at 921.3 nm is evaluated. One future application may be simultaneous determination of the amount of damaging
trace elements and the cement content of the concrete. 相似文献
8.
9.
Markus Follmann Nils Griebenow Michael G. Hahn Ingo Hartung Franz‐Josef Mais Joachim Mittendorf Martina Schfer Hartmut Schirok Johannes‐Peter Stasch Friederike Stoll Alexander Straub Peter Jeschke Ralf Nauen Michael Edmund Beck Hans‐Wilhelm Engels Hans‐Georg Pirkl Reinhard Albers Rolf W. Albach Jens Krause Andreas Hoffmann Holger Casselmann Jeff Dormish 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2013,125(36):9503-9503
10.
Köhler K Förster G Hauser A Dobner B Heiser UF Ziethe F Richter W Steiniger F Drechsler M Stettin H Blume A 《Journal of the American Chemical Society》2004,126(51):16804-16813
The temperature-dependent self-assembly of the single-chain bolaamphiphile dotriacontan-1,1'-diyl-bis[2-(trimethylammonio)ethyl phosphate] (PC-C32-PC) was investigated by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), X-ray scattering, rheological measurements, and dynamic light scattering (DLS). At room temperature this compound, in which two phosphocholine headgroups are connected by a C(32) alkyl chain, proved to be capable of gelling water very efficiently by forming a dense network of nanofibers (Kohler et al. Angew. Chem., Int. Ed. 2004, 43, 245). A specific feature of this self-assembly process is that it is not driven by hydrogen bonds but solely by hydrophobic interactions of the long alkyl chains. The nanofibers have a thickness of roughly the molecular length and show a helical superstructure. A model for the molecular structure of the fibrils which considers the extreme constitution of the bolaamphiphile is proposed. Upon heating the suspensions three different phase transitions can be detected. Above 49 degrees C, the temperature of the main transition where the alkyl chains become "fluid", a clear low-viscosity solution is obtained due to a breakdown of the fibrils into smaller aggregates. Through mechanical stress the gel structure can be destroyed as well, indicating a low stability of these fibers. The gel formation is reversible, but as a drastic rearrangement of the molecules takes place, metastable states occur. 相似文献