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排序方式: 共有680条查询结果,搜索用时 31 毫秒
111.
The study presents an organisational analysis into the linked issues of service productivity and perceived service quality. The operations management literature postulates that a trade-off exists between service productivity and perceived service quality, an assertion which is supported by evidence from managerial experiences and other academic researches. However, is it possible to prevail over the trade-off between productivity and perceived quality? Further, what is the effect of the trade-off on company profitability? To respond to these questions, a retrospective longitudinal study is performed, based on analysis of data collected from 52 offices of a major European banking group over the years 2010–2011. A first analysis verifies the existence of the trade-off. A second then examines the suitability of the employee incentive system intended to overcome the trade-off. Finally, a multiple linear regression model is developed in order to verify whether service productivity and perceived service quality impact on company profitability, and to what extent. 相似文献
112.
Galli U Ercolano E Carraro L Blasi Roman CR Sorba G Canonico PL Genazzani AA Tron GC Billington RA 《ChemMedChem》2008,3(5):771-779
One of the great challenges of medicinal chemistry is to create novel, effective, chemotherapeutic agents that show specificity for cancer cells combined with low systemic toxicity. A novel idea is to target the enzymes of the NAD biosynthesis and recycling pathways given that cancer cells display a higher NAD turnover rate than healthy cells. To this end, the compound FK866 (APO866; (E)-N-[4-(1-benzoylpiperidin-4-yl) butyl]-3-(pyridin-3-yl) acrylamide), which blocks nicotinamide phosphoribosyltransferase (NMPRTase) has entered clinical trials as a potential chemotherapeutic agent. Here we report the synthesis of analogues of FK866 synthesized by click chemistry. 相似文献
113.
Kanaparthi Ramesh Fengxi Chen Armando Borgna Chilukoti Srilakshmi Yi-Fan Han 《Topics in Catalysis》2008,49(3-4):209-215
Manganese oxides supported on mesoporous SBA-15 catalysts have been prepared by molecularly designed dispersion method, using Mn(II) and Mn(III) acetylacetonate organic precursors. XRD and in situ Raman studies demonstrate the formation of highly dispersed Mn2O3 and Mn3O4 nanoparticles on SBA-15 for the calcined samples. The detailed decomposition mechanism was studied by using in situ DRIFTS. Acetylacetonate ligands are stable up to 573 K and can only be completely removed by oxygen treatment. 相似文献
114.
RM Domingues EL Oliveira CS Freire RM Couto PC Simões CP Neto AJ Silvestre CM Silva 《International journal of molecular sciences》2012,13(6):7648-7662
Eucalyptus bark contains significant amounts of triterpenoids with demonstrated bioactivity, namely triterpenic acids and their acetyl derivatives (ursolic, betulinic, oleanolic, betulonic, 3-acetylursolic, and 3-acetyloleanolic acids). In this work, the supercritical fluid extraction (SFE) of Eucalyptus globulus deciduous bark was carried out with pure and modified carbon dioxide to recover this fraction, and the results were compared with those obtained by Soxhlet extraction with dichloromethane. The effects of pressure (100-200 bar), co-solvent (ethanol) content (0, 5 and 8% wt), and multistep operation were studied in order to evaluate the applicability of SFE for their selective and efficient production. The individual extraction curves of the main families of compounds were measured, and the extracts analyzed by GC-MS. Results pointed out the influence of pressure and the important role played by the co-solvent. Ethanol can be used with advantage, since its effect is more important than increasing pressure by several tens of bar. At 160 bar and 40 °C, the introduction of 8% (wt) of ethanol greatly improves the yield of triterpenoids more than threefold. 相似文献
115.
Palle Breistein Jonas Johansson Ismail Ibrahem Shuangzheng Lin Luca Deiana Junliang Sun Armando Cordova 《Advanced Synthesis \u0026amp; Catalysis》2012,354(6):1156-1162
The highly enantioselective cascade reaction between N‐protected α‐cyanoglycine esters and α,β‐unsaturated aldehydes is disclosed. The reaction represents a one‐step entry to polysubstituted 5‐hydroxyproline derivatives having a quaternary α‐stereocenter generally in high yields with up to >95:5 dr and 99:1 er. It is also a direct catalytic two‐step entry to functionalized α‐quaternary proline derivatives. 相似文献
116.
María?Elena?Heras-Ramírez Armando?Quintero-RamosEmail author Alejandro?Alberto?Camacho-Dávila John?Barnard Ricardo?Talamás-Abbud José?Vinicio?Torres-Mu?oz Erica?Salas-Mu?oz 《Food and Bioprocess Technology》2012,5(6):2201-2210
The effects of blanching and drying treatments on stability, physical properties, and antioxidant activity of apple pomace polyphenols were evaluated. Blanched and unblanched apples were extracted, and the pomace was dried in a cabinet dryer at a speed of 3 m/s at 50 °C, 60 °C, 70 °C, and 80 °C. The color, total phenolics, flavonoids, individual polyphenolic compounds, anthocyanins, and total antioxidant activity were analyzed. The blanching process caused a major retention in color, total polyphenolic content, and total flavonoid content for fresh apple pomace when compared with fresh unblanched pomace. Drying of either fresh blanched or fresh unblanched pomace caused a significant reduction (P < 0.05) in total polyphenol and flavonoid content leading to a reduction in the total antioxidant activity. When compared with the unblanched treatment, drying the blanched pomace at 80 °C resulted in a product with significant amounts of total phenolics, flavonoids, and antioxidant activity. The individual phenolic compounds were significantly increased (P < 0.05) in blanched pomace that was not dried when compared with unblanched samples. Drying blanched apple pomace did not cause a significant change in the concentration of individual polyphenolic compounds, but drying unblanched apple pomace caused a reduction in the concentrations of epicatechin and caffeic acid, with an important reduction in p-coumaric acid at temperatures higher than 60 °C. However, the drying process caused a significant reduction in the antioxidant capacity. Therefore, a combination of blanching and drying processes for apple pomace results in a product that maintains antioxidant capacity. 相似文献
117.
Song P Zhao H Manduca A Urban MW Greenleaf JF Chen S 《IEEE transactions on medical imaging》2012,31(9):1821-1832
Fast and accurate tissue elasticity imaging is essential in studying dynamic tissue mechanical properties. Various ultrasound shear elasticity imaging techniques have been developed in the last two decades. However, to reconstruct a full field-of-view 2-D shear elasticity map, multiple data acquisitions are typically required. In this paper, a novel shear elasticity imaging technique, comb-push ultrasound shear elastography (CUSE), is introduced in which only one rapid data acquisition (less than 35 ms) is needed to reconstruct a full field-of-view 2-D shear wave speed map (40 × 38 mm). Multiple unfocused ultrasound beams arranged in a comb pattern (comb-push) are used to generate shear waves. A directional filter is then applied upon the shear wave field to extract the left-to-right (LR) and right-to-left (RL) propagating shear waves. Local shear wave speed is recovered using a time-of-flight method based on both LR and RL waves. Finally, a 2-D shear wave speed map is reconstructed by combining the LR and RL speed maps. Smooth and accurate shear wave speed maps are reconstructed using the proposed CUSE method in two calibrated homogeneous phantoms with different moduli. Inclusion phantom experiments demonstrate that CUSE is capable of providing good contrast (contrast-to-noise ratio ≥ 25 dB) between the inclusion and background without artifacts and is insensitive to inclusion positions. Safety measurements demonstrate that all regulated parameters of the ultrasound output level used in CUSE sequence are well below the FDA limits for diagnostic ultrasound. 相似文献
118.
Armando Arce David H. Covarrubias Marco A. Panduro 《AEUE-International Journal of Electronics and Communications》2012,66(5):349-356
The design of beam-forming networks (BFNs) for a multibeam-steerable antenna array using Coherently Radiating Periodic Structures (CORPS) in cellular mobile communication systems is presented. In this paper, the CORPS technology is introduced and applied to the design of beam-forming networks in cellular systems for the first time. The CORPS-BFNs proposed show improved performance over the common way to feed antenna arrays used in mobile systems. In this design, the input ports of the feeding network design are optimized using the particle swarm optimization (PSO) algorithm. Two 2-beam design configurations of CORPS-BFN for a multibeam-steerable linear array on a cellular scenario are proposed and analyzed. Simulation results show the benefits of BFNs based on CORPS on a cellular mobile scenario based on the array factor response, in terms of side lobe level (SLL) and signal-to-interference (SIR) improvement capability. Furthermore, results for average SIR improvement, signal to interference plus noise power ratio (SINR) and BER are discussed. 相似文献
119.
Alessio Crescitelli Armando Ricciardi Marco Consales Emanuela Esposito Carmine Granata Vincenzo Galdi Antonello Cutolo Andrea Cusano 《Advanced functional materials》2012,22(20):4389-4398
The first evidence of out‐of‐plane resonances in hybrid metallo‐dielectric quasi‐crystal (QC) nanostructures composed of metal‐backed aperiodically patterned low‐contrast dielectric layers is reported. Via experimental measurements and full‐wave numerical simulations, these resonant phenomena are characterized with specific reference to the Ammann‐Beenker (quasi‐ periodic, octagonal) tiling lattice geometry and the underlying physics is investigated. In particular, it is shown that, by comparison with standard periodic structures, a moderately richer spectrum of resonant modes may be excited, due to the easier achievement of phase‐matching conditions endowed by its denser Bragg spectrum. Such modes are characterized by a distinctive plasmonic or photonic behavior, discriminated by their field distribution and dependence on the metal film thickness. Moreover, the response is accurately predicted via computationally affordable periodic‐approximant‐based numerical modeling. The enhanced capability of QCs to control number, spectral position, and mode distribution of hybrid resonances may be exploited in a variety of possible applications. To assess this aspect, label‐free biosensing is studied via characterization of the surface sensitivity of the proposed structures with respect to local refractive index changes. Moreover, it is also shown that the resonance‐engineering capabilities of QC nanostructures may be effectively exploited in order to enhance the absorption efficiency of thin‐film solar cells. 相似文献
120.
A simple and nonexpensive adapted dip-coating technique is presented and used to fabricate arrays of magnetic nanowires with a linear varying height profile. This approach allows controlling the wire height from tenths of nanometers up to several micrometers. Furthermore, the main parameters of this height gradient can be controlled, such as the maximum wire height and the lateral span of the wire array, which can be predicted with excellent accuracy using a proposed analytical model. Moreover, we show that by sequential electrodeposition with dip-coating, arrays of these height varying wires can be grown. This technique represents a novel method to fill porous templates with controlled spatial growth, leading to the fabrication of novel structures and providing control over structural features on the nanoscale level. In particular, the use of these asymmetrically loaded magnetic nanowired substrates to obtain improved microwave nonreciprocal behavior is shown for a microwave phase shifter. 相似文献