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1.
Summary This paper uses Hamiltonian structures to study the problem of the limit of three-dimensional (3D) elastic models to shell
and rod models. In the case of shells, we show that the Hamiltonian structure for a three-dimensional elastic body converges,
in a sense made precise, to that for a shell model described by a one-director Cosserat surface as the thickness goes to zero.
We study limiting procedures that give rise to unconstrained as well as constrained Cosserat director models. The case of
a rod is also considered and similar convergence results are established, with the limiting model being a geometrically exact
director rod model (in the framework developed by Antman, Simo, and coworkers). The resulting model may or may not have constraints,
depending on the nature of the constitutive relations and their behavior under the limiting procedure.
The closeness of Hamiltonian structures is measured by the closeness of Poisson brackets on certain classes of functions,
as well as the Hamiltonians. This provides one way of justifying the dynamic one-director model for shells. Another way of
stating the convergence result is that there is an almost-Poisson embedding from the phase space of the shell to the phase
space of the 3D elastic body, which implies that, in the sense of Hamiltonian structures, the dynamics of the elastic body
is close to that of the shell. The constitutive equations of the 3D model and their behavior as the thickness tends to zero
dictates whether the limiting 2D model is a constrained or an unconstrained director model.
We apply our theory in the specific case of a 3D Saint Venant-Kirchhoff material andderive the corresponding limiting shell and rod theories. The limiting shell model is an interesting Kirchhoff-like shell model
in which the stored energy function is explicitly derived in terms of the shell curvature. For rods, one gets (with an additional
inextensibility constraint) a one-director Kirchhoff elastic rod model, which reduces to the well-known Euler elastica if
one adds an additional single constraint that the director lines up with the Frenet frame.
This paper is dedicated to the memory of Juan C. Simo
This paper was solicited by the editors to be part of a volume dedicated to the memory of Juan Simo. 相似文献
2.
Summary Chiral compounds may be separated by gas chromatography by direct enantiomer separation on optically active stationary phases. More generally the separation can be achieved on conventional stationary phases after formation of diastereoisomeric derivatives. In this work we report on new results in enantiomer separation, indicating that hydrogen bond association is not the only kind of molecular interaction responsible for enantiomer separation. For the separation of a wide variety of chiral compounds with amino or hydroxy groups diastereo-isomeric derivatives may be formed by reaction with L--chlorisovaleryl chloride. The derivatives of amino acids, aliphatic and aromatic amines, amino alcohols and of some alcohols are separated in glass capillaries. Gas chromatography as a separation technique of high selectivity is specifically useful for the separation of mixtures of chemically related components with comparable molecular interactions with the molecules of the stationary phase of a gas chromatographic column. The separation of optically active compounds, particularly, requires highly efficient columns. Glass capillary chromatography is a tool that meets this standard and was applied exclusively in this work. 相似文献
3.
Spatial profiling invertebrate ganglia using MALDI MS 总被引:4,自引:0,他引:4
The ability of MALDI TOF MS to spatially map peptides and proteins directly from a tissue is an exciting advance to imaging mass spectrometry. Recent advances in instrumentation for MS have resulted in instruments capable of achieving several micron spatial resolution while acquiring high-resolution mass spectra. Currently, the ability to obtain high quality mass spectrometric images depends on sample preparation protocols that often result in limited spatial resolution. A number of sample preparation and matrix deposition protocols are evaluated for spatial profiling of Aplysia californica exocrine gland and neuronal tissues. Such samples are different from mammalian tissues, but make good targets for method optimization because of the wealth of biochemical information available on neuropeptide processing and distribution. Electrospray matrix deposition and a variety of freezing methods have been found to be optimum for these invertebrate tissues, with the exact protocols being tissue dependent. 相似文献
4.
5.
Chemiluminescence from the b 0+ → X1 0+ band system of AsI and of the b 0+ → X1 0+, X2 1 systems of SbI in the near-infrared spectral region has been observed in a discharge flow system. Analysis of the spectra led to the spectroscopic constants (in cm?1) of AsI: ωe(X1, X2) = 257 ± 2, ωexe(X1, X2) = 0.82 ± 0.2, Te(b 0+) = 11738 ± 5, ωe(b 0+) = 271 ± 2, ωexe(b 0+) = 0.66 ± 0.2, and of SbI: Te(X2 1) = 965 ± 10, ωe(X1, X2) = 206 ± 6, Te(b 0+) = 12328 ± 10, ωe(b 0+) = 211 ± 6. The intensity ratio of the two sub-systems b 0+ → X2 1 and b 0+→ X1 0+ was found to be ≈0.013 in the case of SbI and ? 0.01 for AsI. 相似文献
6.
Low pressure CO oxidation was studied over small supported Pd particles by means of static secondary ion mass spectrometry (SSIMS). The SSIMS spectra of adsorbed layers on Pd particles with diameters below ~7nm contained, besides other species, Pd n X+ ions (X=C, O, CO;n=1–3). In experiments with Pd films, Pd n C+ species were much less abundant or even absent from the mass spectra. We conclude that CO decomposed in appreciable amounts only on Pd particles. No significant influence of the support material (mica, MgO,α-Al2O3) was seen and posthumous TEM analysis revealed well defined particle morphologies with largely (111) and (100) facets. At total pressures below 10?4 Pa, the relative carbidic intensities Pd n C+/Pd n + , which were taken as proportional to the carbon surface concentrations, first increased with increasing temperatures and then decreased after they passed a maximum at T=400–440 K. The smaller the particle size, the more intense were the maxima. For T ?440 K, carbon was removed from the surface via reaction with oxygen. Strong hysteresis effects in the Cad and COad concentrations occurred during temperature variation measurements. The Pd n C+/Pd n + ratios displayed maxima during heating but not during cooling. While the Pd n CO+/Pd n + ratios were always high at 300 K and always low at T>550 K, they were more intense in the medium temperature range when subjecting the samples to heating. These hysteresis effects are discussed in terms of asymmetric adsorption and reaction behaviour of CO/O2 mixtures, involving inhibition of CO2 formation by adsorbed carbon and carbon monoxide. 相似文献
7.
Lasse Jrgensen Cehofski Anders Kruse Alexander Nrgaard Alsing Benn Falch Sejergaard Jonas Ellegaard Nielsen Anders Schlosser Grith Lykke Sorensen Jakob Grauslund Bent Honor Henrik Vorum 《Molecules (Basel, Switzerland)》2022,27(11)
Aflibercept is a frequently used inhibitor of vascular endothelial growth factor (VEGF) in the treatment of macular edema following central retinal vein occlusion (CRVO). Retinal proteome changes following aflibercept intervention in CRVO remain largely unstudied. Studying proteomic changes of aflibercept intervention may generate a better understanding of mechanisms of action and uncover aspects related to the safety profile. In 10 Danish Landrace pigs, CRVO was induced in both eyes with an argon laser. Right eyes were treated with intravitreal aflibercept while left control eyes received isotonic saline water. Retinal samples were collected 15 days after induced CRVO. Proteomic analysis by tandem mass tag-based mass spectrometry identified a total of 21 proteins that were changed in content following aflibercept intervention. In retinas treated with aflibercept, high levels of aflibercept components were reached, including the VEGF receptor-1 and VEGF receptor-2 domains. Fold changes in the additional proteins ranged between 0.70 and 1.19. Aflibercept intervention resulted in a downregulation of pigment epithelium-derived factor (PEDF) (fold change = 0.84) and endoplasmin (fold change = 0.91). The changes were slight and could thereby not be confirmed with less precise immunohistochemistry and Western blotting. Our data suggest that aflibercept had a narrow mechanism of action in the CRVO model. This may be an important observation in cases when macular edema secondary to CRVO is resistant to aflibercept intervention. 相似文献
8.
The hydrothermal treatment of sugars features a promising technology for the production of fine and platform chemicals from renewable resources. In this work the hydrothermal decomposition of fructose was studied in a buffered medium at a pH range between 2.2 and 8.0. It is demonstrated that at lower pH values mainly 5-hydroxymethylfurfural (HMF), levulinic acid and humin are generated, while lactic acid and acetic acid are produced at higher pH values. The work shows that the use of moderate acidic conditions may have advantages for the hydrothermal HMF production over the use of strongly acidic conditions, as especially the degradation into levulinic acid is suppressed. Besides, this study deals with a rather complex reaction network, hence limitations and need for adaption of the kinetic model are discussed. 相似文献
9.
Prof. Pil Seok Chae Andrew C. Kruse Dr. Kamil Gotfryd Rohini R. Rana Kyung Ho Cho Prof. Søren G. F. Rasmussen Hyoung Eun Bae Richa Chandra Prof. Ulrik Gether Prof. Lan Guan Prof. Brian K. Kobilka Prof. Claus J. Loland Dr. Bernadette Byrne Prof. Samuel H. Gellman 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(46):15645-15651
Integral membrane proteins play central roles in controlling the flow of information and molecules across membranes. Our understanding of membrane protein structures and functions, however, is seriously limited, mainly due to difficulties in handling and analysing these proteins in aqueous solution. The use of a detergent or other amphipathic agents is required to overcome the intrinsic incompatibility between the large lipophilic surfaces displayed by the membrane proteins in their native forms and the polar solvent molecules. Here, we introduce new tripod amphiphiles displaying favourable behaviours toward several membrane protein systems, leading to an enhanced protein solubilisation and stabilisation compared to both conventional detergents and previously described tripod amphiphiles. 相似文献
10.
Prof. Pil Seok Chae Prof. Søren G. F. Rasmussen Rohini R. Rana Kamil Gotfryd Andrew C. Kruse Aashish Manglik Kyung Ho Cho Shailika Nurva Prof. Ulrik Gether Prof. Lan Guan Prof. Claus J. Loland Dr. Bernadette Byrne Prof. Brian K. Kobilka Prof. Samuel H. Gellman 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(16):4964-4964