We derive a one-dimensional model for an elastic shuttle, that is, a thin rod with rounded ends and small fixed terminals, by means of an asymptotic procedure of dimension reduction. In the model, deformation of the shuttle is described by a system of ordinary differential equations with variable degenerating coefficients, and the number of the required boundary conditions at the end points of the one-dimensional image of the rod depends on the roundness exponent m∈(0,1). Error estimates are obtained in the case m∈(0,1/4) by using an anisotropic weighted Korn inequality, which was derived in an earlier paper by the authors. We also briefly discuss boundary layer effects, which can be neglected in the case m∈(0,1/4) but play a crucial role in the formulation of the limit problem for m ≥ 1/4. 相似文献
A novel dihydroflavonol, C-6,O-7-dimethylaromadendrin, was isolated from a 70% aqueous acetone extract of pine (Pinus sylvestris L.) bark. Its structure was determined by high-resolution negative fast atom bombardment mass spectrometry and NMR spectroscopy. The complete assignment of proton and carbon signals was achieved by 2D NMR experiments: HSQC, HMBC, DQF-COSY and NOESY. 相似文献
Here, an unidentified type of micropillar growth is described at room temperature during conventional direct‐current magnetron sputtering (DC‐MS) deposition from a Li4Ti5O12+graphite sputter target under negative substrate bias and high operating pressure. These fabricated carbon–Li2O–TiO2 microstructures consisting of various Li4Ti5O12/Li2TiO3/LixTiO2 crystalline phases are demonstrated as an anode material in Li‐ion microbatteries. The described micropillar fabrication method is a low‐cost, substrate independent, single‐step, room‐temperature vacuum process utilizing a mature industrial complementary metal–oxide–semiconductor (CMOS)‐compatible technology. Furthermore, tentative consideration is given to the effects of selected deposition parameters and the growth process, as based on extensive physical and chemical characterization. Additional studies are, however, required to understand the exact processes and interactions that form the micropillars. If this facile method is further extended to other similar metal oxide–carbon systems, it could offer alternative low‐cost fabrication routes for microporous high‐surface area materials in electrochemistry and microelectronics. 相似文献
Greater stability of liposome coatings and improved resolution of model steroids in capillary electrochromatography (CEC) were sought by adding small diamines (ethylenediamine, diaminopropane, bis-tris-propane, or N-(2-hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid, HEPES)) to the liposome solution before coating of fused silica capillaries. The phospholipid coatings consisted of 1 mM of 8:2 mol% phosphatidylcholine (PC)/phosphatidylserine (PS) and 5 mM of modifier in buffer solutions (acetate, phosphate, or Tris) at pH 4.0-7.4. The coating was based on a published procedure, and five steroids were used as neutral model analytes in evaluation of the coating. The results showed that under optimal conditions, the small linear diamines increased the packing density of anionic phospholipids, leading to improved separations. In addition, the choice of buffer for the liposome coating and separation appeared to influence the performance of the coatings. While buffers with amino groups take part in the phospholipid bilayer formation, buffers like phosphate may even have negative effect on coating formation. The factors affecting phospholipid coatings with diamines as modifiers are clarified. 相似文献
The feasibility of ultra thin-layer chromatography atmospheric pressure matrix-assisted laser desorption ionization mass spectrometry (UTLC-AP-MALDI-MS) has been studied in the analysis of small molecules. Because of a thinner adsorbent layer, the monolithic UTLC plates provide 10-100 times better sensitivity in MALDI analysis than conventional high performance thin-layer chromatography (HPTLC) plates. The limits of detection down to a low picomole range are demonstrated by UTLC-AP-MALDI-MS. Other advantages of UTLC over HPTLC include faster separations and lower solvent consumption. The performances of AP-MALDI-MS and vacuum MALDI-MS have been compared in the analysis of small drug molecules directly from the UTLC plates. The desorption from the irregular surface of UTLC plates with an external AP-MALDI ion source combined with an ion trap instrument provides clearly less variation in measurements of m/z values when compared with a vacuum MALDI-time-of-flight (TOF) instrument. The performance of the UTLC-AP-MALDI-MS method has been applied successfully to the purity analysis of synthesis products produced by solid-phase parallel synthesis method. 相似文献
The metathetical reactions of a) [Li(tmeda)]2[(S)C(PPh2S)2] (Li2? 3 c ) with CuCl2 and b) [Li(tmeda)]2[(SPh2P)2CSSC(PPh2S)2] (Li2? 4 c ) with two equivalents of CuCl both afford the binuclear CuI complex {Cu2[(SPh2P)2CSSC(PPh2S)2]} ( 5 c ). The elongated (C)S? S(C) bond (ca. 2.54 and 2.72 Å) of the dianionic ligand observed in the solid‐state structure of 5 c indicate the presence of diradical character as supported by theoretical analyses. The treatment of [Li(tmeda)]2[(SPh2P)2CSeSeC(PPh2S)2] (Li2? 4 b ) and Li2? 4 c with AgOSO2CF3 produce the analogous AgI derivatives, {Ag2[(SPh2P)2CEEC(PPh2S)2]} ( 6 b , E=Se; 6 c , E=S), respectively. The diselenide complex 6 b exhibits notably weaker Ag? Se(C) bonds than the corresponding contacts in the CuI congeners, and the 31P NMR data suggest a possible isomerization in solution. In contrast to the metathesis observed for CuI and AgI reagents, the reactions of Li2? 4 b and Li2? 4 c with Au(CO)Cl involve a redox process in which the dimeric dichalcogenide ligands are reduced to the corresponding monomeric dianions, [(E)C(PPh2S)2]2? ( 3 b , E=Se; 3 c , E=S), and one of the gold centers is oxidized to generate the mixed‐valent AuI/AuIII complexes, {Au[(E)C(PPh2S)2]}2 ( 7 b , E=Se; 7 c , E=S), with relatively strong aurophilic AuI???AuIII interactions. The new compounds 5 c , 6 b , c and 7 b , c are characterized in solution by NMR spectroscopy and in the solid state by X‐ray crystallography ( 5 c , 6 b , 7 b and 7 c ) and by Raman spectroscopy ( 5 c and 6 c ). The UV‐visible spectra of coinage metal complexes of the type 5 , 6 and 7 are discussed in the light of results from theoretical analyses using time‐dependent density functional theory. 相似文献
The development of a highly sensitive, selective, and efficient sensor for the determination and detection of Cr(III) ions remains a great challenge. Recently, some fluorescent chemosensors have been developed for the recognition of Cr(III) ions. But, the main drawbacks of the reported fluorescent chemosensors are the lack of selectivity and interference of anions and other trivalent cations. Herein, we designed and synthesized a novel thiazole-based fluorescent and colorimetric Schiff base chemosensor SB2 for the detection of Cr(III) ion by chemodosimetric approach. Using different analytical techniques including UV–vis, 13C-NMR, 1H-NMR, and FT-IR analysis the chemosensor SB2 was structurally characterized. The fully characterized chemosensor SB2 was used for the spectrofluorimetric and colorimetric detection of Cr(III) ions. Interestingly, chemosensor SB2 upon interaction with various metal cations including Ni2+, Na+, Cd2+, Ag+, Mn2+, K+, Zn2+, Cu2+, Hg2+, Co2+, Pb2+, Mg2+, Sn2+, Al3+ and Cr3+ displays highly selective and sensitive fluorescent (turn-on) and colorimetric (yellow to colorless) response toward Cr(III) ions. The fluorescence and UV–vis techniques confirmed the selective hydrolysis of azomethine group (-C?=?N-) of Schiff base chemosensor SB2 by Cr(III) ions. As a result, the fluorescence enhancement was observed that is corresponding to 2-hydroxy-1-nepthaldehyde (fluorophore). The chemosensor SB2 exhibits high interference performance towards Cr(III) ions over other metal cations in a wide pH range. Mover, the quite low detection limit was calculated to be 0.027 µg ml-1 (0.5 µM) (3σ/slop), lower than the maximum tolerable limits of Cr(III ions (10 µM) in drinking water permitted by the United States Environmental Protection Agency (EPA). These results show that chemosensor SB2 has great potential to detect selectively Cr(III) ions in the agricultural, environmental and biological analysis system.
Big Data on electronic records of social interactions allow approaching human behaviour and sociality from a quantitative point of view with unforeseen statistical power. Mobile telephone Call Detail Records (CDRs), automatically collected by telecom operators for billing purposes, have proven especially fruitful for understanding one-to-one communication patterns as well as the dynamics of social networks that are reflected in such patterns. We present an overview of empirical results on the multi-scale dynamics of social dynamics and networks inferred from mobile telephone calls. We begin with the shortest timescales and fastest dynamics, such as burstiness of call sequences between individuals, and “zoom out” towards longer temporal and larger structural scales, from temporal motifs formed by correlated calls between multiple individuals to long-term dynamics of social groups. We conclude this overview with a future outlook. 相似文献