Herein, we report the preparation of bridged tetrahydrobenzo[b]azepines, which was accomplished through an aza‐Piancatelli cyclization/Michael addition sequence in a one‐pot fashion from readily available precursors. It is noteworthy that a general method to access these scaffolds was hitherto unprecedented. Additionally, the multifaceted aspects of this process have been exemplified through its application to the synthesis of 2‐azabicyclo[3.2.1]octanes and bridged tetrahydrobenzo[b]oxepines, along with post‐derivatizations. 相似文献
Dye‐sensitized solar cells (DSSCs) based on CuII/I bipyridyl or phenanthroline complexes as redox shuttles have achieved very high open‐circuit voltages (VOC, more than 1 V). However, their short‐circuit photocurrent density (JSC) has remained modest. Increasing the JSC is expected to extend the spectral response of sensitizers to the red or NIR region while maintaining efficient electron injection in the mesoscopic TiO2 film and fast regeneration by the CuI complex. Herein, we report two new D‐A‐π‐A‐featured sensitizers termed HY63 and HY64 , which employ benzothiadiazole (BT) or phenanthrene‐fused‐quinoxaline (PFQ), respectively, as the auxiliary electron‐withdrawing acceptor moiety. Despite their very similar energy levels and absorption onsets, HY64 ‐based DSSCs outperform their HY63 counterparts, achieving a power conversion efficiency (PCE) of 12.5 %. PFQ is superior to BT in reducing charge recombination resulting in the near‐quantitative collection of photogenerated charge carriers. 相似文献
This study aims to experimentally examine the energy-saving potential by using R-134a filled separated two-phase thermosiphon loop (STPTL) for data center applications. A parametric study had been made to compare the energy consumption of two data center racks. Two fin-and-tube heat exchangers were attached to one of the racks to form two individual thermosiphon loops. The experiments were carried out subject to different operating conditions, including three ambient temperatures (20 °C, 23 °C, and 27 °C) and filling ratios ranging from 30 to 90% in association with heating loads ranging between 1.5 kW and 6 kW. Parametric influences regarding concentrated heat loading or uniform heat loading are studied. It was found that an appreciable energy-savings can be obtained at high filling ratios and a maximum of 49% energy-saving with the assistance of thermosiphon is observed. Accordingly, the rising of system pressure will result in noticeable savings. Relative to the uniform heat loading of the data rack, the thermosiphon shows even more energy-saving potential in concentrated heat loading. This phenomenon is more pronounced at a lower ambient temperature like 20 °C. On the other hand, there is no appreciable energy-saving for the thermosiphon between concentrated and uniform heating loads when the ambient temperature is high (27 °C). Furthermore, the influence of airflow rate was also investigated under various ambient temperatures with a 90% filling ratio and a heating load of 6 kW. The results revealed that the lower airflow rate in the thermosiphon yields comparatively better energy-saving than the higher flow rate. The study on the influence of using two STPTLs indicated that 15–23% energy-saving can be achieved at a 90% filling ratio and 6 kW heating load for all the studied ambient conditions if compared with testing each loop separately. Lower thermal resistance is seen at the higher filling ratios, ambient temperatures, and heating loads.
The double crossover junction (DX) is a fundamental building block for generating complex and varied structures from DNA. However, its implementation in functional devices is limited to the inherent properties of DNA itself. Here, we developed design strategies to generate the first metal–DX DNA tiles (DXM) by site‐specifically functionalizing the tile crossovers with tetrahedral binding pockets that coordinate CuI. These DX junctions bind two CuI ions independently at distinct sites, display greater thermal stability than native DX tiles upon metalation, and melt in a cooperative fashion. In addition, the right‐handed helical chirality of DNA is transferred to the metal centers. Our tiles display high metal ion selectivity, such that CuII is spontaneously reduced to CuI in situ. By modifying our design over three generations of tiles, we elucidated the thermodynamic and geometric requirements for the successful assembly of DXM tiles, which have direct applicability in developing robust, stable DNA‐based materials with electroactive, photoactive, and catalytic properties. 相似文献
Phosphorus dialdehydes RP (OC6H4CHO)2 (R = Ph, Me2N) react with phosphodihydrazides PhP(Y)-[N(CH3)NH2]2 (Y = S, O) to give macrocycles 6a–c arising from [2 + 2] cyclocondensation reactions. Treatment of phosphodihydrazone PhP(S) [OC6H4CH N–N(Me)H]2 7 with phenyldichlorophosphine affords macrocycle 8 possessing tri and tetracoordinated phosphorus atoms. Clean desulfurization of thiophosphorus macrocycles 9 and 12 gives rise selectively to new tricoordinated phosphorus containing macrocycles 11 and 13 . 相似文献
Nelumbo nucifera Gaertn., or the so-called sacred lotus, is a useful aquatic plant in the Nelumbonaceae family that has long been used to prepare teas, traditional medicines as well as foods. Many studies reported on the phytochemicals and biological activities of its leaves and seeds. However, to date, only few studies were conducted on its stamen, which is the most important ingredient for herbal medicines, teas and other phytopharmaceutical products. Thus, this present study focuses on the following: (1) the application of high-performance liquid chromatography with photodiode array detection for a validated separation and quantification of flavonoids from stamen; (2) the Nelumbo nucifera stamen’s in vitro and in cellulo antioxidant activities; as well as (3) its potential regarding the inhibition of skin aging enzymes for cosmetic applications. The optimal separation of the main flavonoids from the stamen ethanolic extract was effectively achieved using a core-shell column. The results indicated that stamen ethanolic extract has higher concentration of in vitro and in cellulo antioxidant flavonoids than other floral components. Stamen ethanolic extract showed the highest protective effect against reactive oxygen/nitrogen species formation, as confirmed by cellular antioxidant assay using a yeast model. The evaluation of potential skin anti-aging action showed that the stamen extract has higher potential to inhibit tyrosinase and collagenase compared with its whole flower. These current findings are the first report to suggest the possibility to employ N. nucifera stamen ethanolic extract as a tyrosinase and collagenase inhibitor in cosmetic applications, as well as the utility of the current separation method. 相似文献
The present work focuses on studying the contribution of the Auger electron emission in proton-induced interactions in biological matter. The Monte Carlo track-structure code, TILDA-V, was then used for modeling the protons beams of 10 keV to 100 MeV in biological matter, namely, water vapor and hydrated DNA. The main ionizing processes are described by means of an extensive set of ab initio differential and total cross sections computed within a quantum-mechanical CDW-EIS approximation. 相似文献