Many animals regulate power generation for locomotion by varying the number of muscle fibers used for movement. However, insects with asynchronous flight muscles may regulate the power required for flight by varying the calcium concentration ([Ca(2+)]). In vivo myoplasmic calcium levels in Drosophila flight muscle have been found to vary twofold during flight and to correlate with aerodynamic power generation and wing beat frequency. This mechanism can only be possible if [Ca(2+)] also modulates the flight muscle power output and muscle kinetics to match the aerodynamic requirements. We found that the in vitro power produced by skinned Drosophila asynchronous flight muscle fibers increased with increasing [Ca(2+)]. Positive muscle power generation started at pCa = 5.8 and reached its maximum at pCa = 5.25. A twofold variation in [Ca(2+)] over the steepest portion of this curve resulted in a two- to threefold variation in power generation and a 1.2-fold variation in speed, matching the aerodynamic requirements. To determine the mechanism behind the variation in power, we analyzed the tension response to muscle fiber-lengthening steps at varying levels of [Ca(2+)]. Both calcium-activated and stretch-activated tensions increased with increasing [Ca(2+)]. However, calcium tension saturated at slightly lower [Ca(2+)] than stretch-activated tension, such that as [Ca(2+)] increased from pCa = 5.7 to pCa = 5.4 (the range likely used during flight), stretch- and calcium-activated tension contributed 80% and 20%, respectively, to the total tension increase. This suggests that the response of stretch activation to [Ca(2+)] is the main mechanism by which power is varied during flight.

This article presents a new microporous tube-in-tube microchannel reactor (MTMCR) with high throughput and excellent micromixing performance. In the MTMCR, one liquid from the inner tube is divided into many liquid fragments through the microscale pores in the walls, and then these fragments vertically collide with another flowing annular liquid sheet between the inner and outer tubes, generating cross-flow. The annular microchannel allows a mass of fluid to go through it rapidly without enlarging the channel width, thereby achieving a throughput as high as 9 L/min (typical microreactor throughput = 4−100 mL/min). Furthermore, the micromixing performance is expressed in terms of a segregation index, which can be as low as 0.0007. The micromixing time evaluated by the incorporation model reaches the magnitude of milliseconds. In addition, several factors affecting the micromixing such as reactant concentration, flow rate, volume flow ratio, micropore size, and channel width were investigated. The results indicated that an increase of the flow rate, as well as a reduction of the micropore size and channel width, could greatly intensify the micromixing. Therefore, it can be envisioned that the MTMCR would exhibit great potential for various industrial applications in the future.

The first enantioselective chiral phosphoric acid-catalyzed transfer hydrogenation of unprotected ortho-hydroxyaryl alkyl N-H ketimines using Hantszch di-tert-butyl ester as a reductant is reported. A variety of ortho-hydroxybenzylamines were obtained in good to excellent yields and enantiomeric excesses.

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In the presence of ac atalytic amount of iron(III) acetylacetonate [Fe(acac) 3 ], the reaction of structurally diverse ketoxime esters with trimethylsilyl azide (TMSN 3 )a fforded g-azido ketones in good to excellent yields. This unprecedented distal g-C(sp 3 )ÀHb ond azidation reaction went through as equence of reductiveg eneration of an iminyl radical, 1,5-hydrogen atom transfer (1,5-HAT) and iron-mediated redox azido transfert ot he translocated carbon radical. TMSN 3 served not only as an itrogen source to functionalise the unactivated C(sp 3 )ÀHb ond, but also as ar eductant to generate the catalytically active Fe II species in situ. Based on the same principle, an ovel b-C(sp 3 )ÀHf unctionalisation of alcohols via N-acyloxy imidates was subsequently realised, leading, after hydrolysis of the resulting ester,t ob-azido alcohols, which are important building blocks in organic and medicinal chemistry.