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1.
This paper focuses on MOOCs (massive open online courses), a fairly recent paradigm in e-learning educational projects. Despite the high dropout rate, and 相似文献
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Microwave irradiation facilitated the synthesis of 4-arylthio-3-oxazolin-5-ones from ethyl cyanoformate, thiophenol, and cyclic ketones. Subsequent decarboxylation and in situ [3+2] cycloaddition provided novel 2,3,4,5-tetrahydro-1H-pyrrolo[1,2-c][1,3]diazepine scaffolds after a spontaneous retro-Mannich domino reaction. 相似文献
5.
Rois Benassi Erika Ferrari Sandra Lazzari Francesca Pignedoli Ferdinando Spagnolo Monica Saladini 《Journal of Physical Organic Chemistry》2011,24(4):299-310
In the present study, we investigate the structures of glucosylated curcumin derivatives with DFT at B3LYP/6‐31G* level. A conformational analysis is performed in order to determine the conformational minimum (GS) and rotational transition state (TS) of curcumin derivatives and then their electronic features are evaluated. HOMO and LUMO frontier orbitals and maps of electron density potential (MEPs) are plotted and compared. In order to correlate their predicted spectroscopic properties with IR, UV–vis and NMR experimental data we extended the theoretical study on electronic properties to different solvents (H2O, MeOH, ACN, DMSO). The main finding is that the curcuminic core maintains the same geometrical and electronic structures in all compounds miming the metal coordination capability showed by curcumin. Therefore, we may confirm that the presence of glucose does not affect the electronic properties of the derivatives. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
6.
In Charikar et al. (J. Comput. Syst. Sci. 64(4):785–819, 2002) the authors proposed a new model for studying the function evaluation problem based on a variant of the classical decision
tree problem for Boolean functions. In this variant each variable of the function to evaluate has an associated cost which
has to be paid in order to read the value of the variable. Given a function f and an assignment σ to the variables of f, the performance of an algorithm for evaluating f is measured via the competitive ratio, i.e., the ratio of the total cost spent by the algorithm and the cost of the cheapest
set of variables constituting a certificate for the value of the function on the given assignment. 相似文献
7.
Michele Conti Michele Marconi Giulia Campanile Alessandro Reali Daniele Adami Raffaella Berchiolli Ferdinando Auricchio 《Meccanica》2017,52(3):633-644
Nitinol self-expanding stents are used for the endovascular management of peripheral artery diseases of the popliteal artery, which is located behind the knee joint. Unfortunately, the complex kinematics of the artery during the leg flexion leads to severe loading conditions, favouring the mechanical failure of the stent, calling for a specific biomechanical analysis. For this reason, in the present study we reconstruct by medical image analysis the patient-specific popliteal kinematics during leg flexion, which is subsequently exploited to compute the mechanical response of a stent model, virtually implanted in the artery by structural finite element analysis (FEA). The medical image analysis indicates a non-uniform configuration change of the artery during the leg flexion, leading to an increase of the vessel curvature above the knee. The computed mechanical response of the stent reflects the non-uniform configuration change of the artery as after the flexion the average stress is higher in the part of the stent located above the knee. Although the proposed analysis is limited to a case-study, it shows the capability of patient-specific FEA simulations to compute the mechanical response of a stent model subjected to the complex and severe loading conditions of the popliteal artery during leg flexion. 相似文献
8.
Curcumin, a chemical compound present in the well-known Indian spice turmeric, has uses in many different fields ranging from
medicinal chemistry to the dye industry. Its poor water solubility, though, makes Curcumin difficult to handle, making it
less appealing for potential uses. The principal aim of this work is to perform a computational study of the structural and
electronic properties of Curcumin {IUPAC name: 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione} in several solvents,
and a comparison with experimental data. Rotameric equilibria, vibrational and thermochemical analysis, and electronic absorption
spectra (with ab initio and semi-empirical methodologies) have been studied, both in vacuum and in three selected solvents. Different computational
techniques have been applied and the results compared. Combined approaches resulted in very satisfactory results. Interesting
results have emerged, which suggest subsequent investigations about the nature of the excited states and potential derivatives
of Curcumin that possibly have non-linear optical applications, as a π-core for innovative materials in laser engineering and photonics. 相似文献
9.
The enzyme horseradish peroxidase (HRP) was used to polymerize acid‐functionalized anilines to make self‐doped polymer in the presence of a polycationic template. Anionic templates such as sulfonated polystyrene (SPS) could not function as a suitable template for the polymerization of acid‐functionalized aniline derivatives. Several types of polyelectrolytes were used as templates to observe the structural effects and doping behavior of polyaniline/template complexes. The synthesis is straightforward and the conditions are mild in that the polymerization of conducting polyanilines may be carried out in buffered solutions as high as pH 6, with a stoichiometric amount of hydrogen peroxide and catalytic amount of enzyme. The conductivity of these enzymatically synthesized self‐doped polymers was relatively high without additional doping due to the self‐doping of the acid moieties. The conductivity did not decrease dramatically at pH 3 as is the usual case of unsubstituted HCl‐doped polyaniline and maintained good conductivity even at pH 6. The measured conductivity at pH 4~pH 6 is around 10?4 S/cm to 10?6 S/cm. 相似文献
10.
Whereas the Diels-Alder reaction has been in vogue as a facile method of six-membered ring construction for many years, its application to a one-step cis-octalone synthesis was precluded by discouraging, early reports on the conditions required for the interaction of dienes with 2-cyclohexenones and on the yields of the resultant adducts.1,2 It is quite conceivable that these observations were responsible in part for the minimization of use of an otherwise attractive route toward angularly alkylated six-membered polycycles in the field of steroid total synthesis. The discovery of Lewis acid catalysis of the cycloaddition of α, β-unsaturated carbonyl compounds3 has rekindled interest in the above reactions.4 The following discussion illustrates octalone 相似文献