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101.
102.
The absorption and emission properties of rhodamine 101 in polar, aprotic propionitrile-butyronitrile (4:5 v/v) solvent have been investigated. The equilibrium between the neutral zwitterionic and lactonic (colourless) forms is strongly affected by the temperature in the range 293–144 K. In dilute solution (1.12×10−5M), at room temperature the lactonic form is 98%, while at 144 K the zwitterionic form predominates, being 79%. These findings are discussed in terms of differential stabilization of the lactonic and zwitterionic forms through non-specific solute-solvent interactions involving the COO−1 group.  相似文献   
103.
DFT calculations have been carried out to describe the pathway of a sodium ion along the stacking direction of a tubular structure set up by five cyclopeptidic units, which can be considered a suitable model of a hollow tubular structure of indefinite length. A lattice of points inside the tubular structure is defined and the DFT interaction energy values with a sodium ion are obtained. The data allow predicting a zigzag path of the ion inside the hosting structure.  相似文献   
104.
In this paper we apply the similarity methods to a modified Korteweg-deVries equation containing an arbitrary function of time which describes the inhomogeneity effects. Some classes of functional forms for this arbitrary function are characterized and the related similarity solutions are determined.  相似文献   
105.
106.
A semi-analytical finite element (SAFE) method is presented for analyzing the wave propagation in viscoelastic axisymmetric waveguides. The approach extends a recent study presented by the authors, in which the general SAFE method was extended to account for material damping. The formulation presented in this paper uses the cylindrical coordinates to reduce the finite element discretization over the waveguide cross-section to a mono-dimensional mesh. The algorithm is validated by comparing the dispersion results with viscoelastic cases for which a Superposition of Partial Bulk Waves solution is known. The formulation accurately predicts dispersion properties and does not show any missing root. Applications to viscoelastic axisymmetric waveguides with varying mechanical and geometrical properties are presented.  相似文献   
107.
The first highly enantioselective arylogous Michael reaction (AMR) of 3-unsubstituted phthalides has been described. This phase-transfer methodology, which uses catalytic amounts of KOH/18-crown-6 catalyst in mesitylene in the presence of N,O-bis(trimethylsilyl)acetamide (BSA), gives access to a broad range of 3-monosubstituted phthalides with high levels of syn diastereoselectivity and good yields, starting from 3-unsubstituted derivatives and diverse α,β-unsaturated carbonyl compounds. The reaction also applies to unactivated 3-alkyl phthalides to afford 3,3-dialkyl derivatives. A plausible mechanism has been suggested. DFT analysis of possible transition states gives a rationale of the high syn diastereoselectivity observed and its correlation with the solvent's dielectric constant.  相似文献   
108.
<正>Water and related systems play a central role in science and technology. Although water has unusual and anomalous behaviors,if compared with normal liquids, it is of fundamental interest in many research fields going from chemical-physics to life sciences. The first and well known example of these anomalies is the density maximum, at 277 K, intuited by Galilei [1] in 1612and lately discovered in Florence [2].  相似文献   
109.
S. Samani  Farhad  Molaie  Moslem  Pellicano  Francesco 《Meccanica》2019,54(7):1071-1081
Meccanica - The issue of gear noise is fairly common in power transmission systems. This noise largely stems from the gear pairs vibration triggered by transmission error excitation. This is mainly...  相似文献   
110.
Ricerche di Matematica - This paper provides an account of results and methods from the theory of infinite groups admitting only finitely many normalizers of subgroups with a given property. Some...  相似文献   
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