Catalytic Enantioconvergent Couplings of Secondary and Tertiary Electrophiles with Olefins

Carbon–carbon bonds, including those between sp^3-hybridized carbon atoms (alkyl–alkyl bonds), typically comprise much of the framework of organic molecules. In the case of s^p3-hybridized carbon, the carbon can be stereogenic and the particular stereochemistry can have implications for structure and function. As a consequence, the development of methods that simultaneously construct alkyl–alkyl bonds and control stereochemistry is important, although challenging. Here we describe a strategy for enantioselective alkyl–alkyl bond formation, in which a racemic alkyl electrophile is coupled with an olefin in the presence of a hydrosilane, through the action of a chiral nickel catalyst. We demonstrate that families of racemic alkyl halides—including secondary and tertiary electrophiles, which have not previously been shown to be suitable for enantioconvergent coupling with alkyl metal nucleophiles—cross-couple with olefins with good enantioselectivity and yield under very mild reaction conditions. Given the ready availability of olefins, our approach opens the door to developing more general methods for enantioconvergent alkyl–alkyl coupling

Simulation analysis of UAV autonomous landing system based on TECs

Aiming at the decoupling control problem of velocity and altitude in the process of unmanned aerial vehicles (UAV) autonomous landing under visual guidance, this paper establishes the fl ight control model of fi xed wing UAV, and deduces the coupling relationship between airspeed and altitude in the process of UAV glide, The total energy control system (TECs) is used for decoupling control to realize the autonomous fi xed-point landing of UAV. The simulation results show that the designed control law can decouple the airspeed and altitude of the UAV, so that the UAV can land at the predetermined place autonomously and accurately

Dynamic Hand Gesture-Featured Human Motor Adaptation in Tool Delivery using Voice Recognition

Human-robot collaboration has benefited users with higher efficiency towards interactive tasks. Nevertheless, most collaborative schemes rely on complicated human-machine interfaces, which might lack the requisite intuitiveness compared with natural limb control. We also expect to understand human intent with low training data requirements. In response to these challenges, this paper introduces an innovative human-robot collaborative framework that seamlessly integrates hand gesture and dynamic movement recognition, voice recognition, and a switchable control adaptation strategy. These modules provide a user-friendly approach that enables the robot to deliver the tools as per user need, especially when the user is working with both hands. Therefore, users can focus on their task execution without additional training in the use of human-machine interfaces, while the robot interprets their intuitive gestures. The proposed multimodal interaction framework is executed in the UR5e robot platform equipped with a RealSense D435i camera, and the effectiveness is assessed through a soldering circuit board task. The experiment results have demonstrated superior performance in hand gesture recognition, where the static hand gesture recognition module achieves an accuracy of 94.3\%, while the dynamic motion recognition module reaches 97.6\% accuracy. Compared with human solo manipulation, the proposed approach facilitates higher efficiency tool delivery, without significantly distracting from human intents.Comment: This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Learning Diverse Tone Styles for Image Retouching

Image retouching, aiming to regenerate the visually pleasing renditions of given images, is a subjective task where the users are with different aesthetic sensations. Most existing methods deploy a deterministic model to learn the retouching style from a specific expert, making it less flexible to meet diverse subjective preferences. Besides, the intrinsic diversity of an expert due to the targeted processing on different images is also deficiently described. To circumvent such issues, we propose to learn diverse image retouching with normalizing flow-based architectures. Unlike current flow-based methods which directly generate the output image, we argue that learning in a style domain could (i) disentangle the retouching styles from the image content, (ii) lead to a stable style presentation form, and (iii) avoid the spatial disharmony effects. For obtaining meaningful image tone style representations, a joint-training pipeline is delicately designed, which is composed of a style encoder, a conditional RetouchNet, and the image tone style normalizing flow (TSFlow) module. In particular, the style encoder predicts the target style representation of an input image, which serves as the conditional information in the RetouchNet for retouching, while the TSFlow maps the style representation vector into a Gaussian distribution in the forward pass. After training, the TSFlow can generate diverse image tone style vectors by sampling from the Gaussian distribution. Extensive experiments on MIT-Adobe FiveK and PPR10K datasets show that our proposed method performs favorably against state-of-the-art methods and is effective in generating diverse results to satisfy different human aesthetic preferences. Source code and pre-trained models are publicly available at https://github.com/SSRHeart/TSFlow

Catalytic Enantioconvergent Couplings of Secondary and Tertiary Electrophiles with Olefins

Carbon–carbon bonds, including those between sp^3-hybridized carbon atoms (alkyl–alkyl bonds), typically comprise much of the framework of organic molecules. In the case of s^p3-hybridized carbon, the carbon can be stereogenic and the particular stereochemistry can have implications for structure and function. As a consequence, the development of methods that simultaneously construct alkyl–alkyl bonds and control stereochemistry is important, although challenging. Here we describe a strategy for enantioselective alkyl–alkyl bond formation, in which a racemic alkyl electrophile is coupled with an olefin in the presence of a hydrosilane, through the action of a chiral nickel catalyst. We demonstrate that families of racemic alkyl halides—including secondary and tertiary electrophiles, which have not previously been shown to be suitable for enantioconvergent coupling with alkyl metal nucleophiles—cross-couple with olefins with good enantioselectivity and yield under very mild reaction conditions. Given the ready availability of olefins, our approach opens the door to developing more general methods for enantioconvergent alkyl–alkyl coupling

Effects of aging and macrophages on mice stem Leydig cell proliferation and differentiation in vitro

BackgroundTestosterone plays a critical role in maintaining reproductive functions and well-beings of the males. Adult testicular Leydig cells (LCs) produce testosterone and are generated from stem Leydig cells (SLCs) during puberty through adulthood. In addition, macrophages are critical in the SLC regulatory niche for normal testicular function. Age-related reduction in serum testosterone contributes to a number of metabolic and quality-of-life changes in males, as well as age-related changes in immunological functions. How aging and testicular macrophages may affect SLC function is still unclear.MethodsSLCs and macrophages were purified from adult and aged mice via FACS using CD51 as a marker protein. The sorted cells were first characterized and then co-cultured in vitro to examine how aging and macrophages may affect SLC proliferation and differentiation. To elucidate specific aging effects on both cell types, co-culture of sorted SLCs and macrophages were also carried out across two ages.ResultsCD51+ (weakly positive) and CD51++ (strongly positive) cells expressed typical SLC and macrophage markers, respectively. However, with aging, both cell types increased expression of multiple cytokine genes, such as IL-1b, IL-6 and IL-8. Moreover, old CD51+ SLCs reduced their proliferation and differentiation, with a more significant reduction in differentiation (2X) than proliferation (30%). Age matched CD51++ macrophages inhibited CD51+ SLC development, with a more significant reduction in old cells (60%) than young (40%). Crossed-age co-culture experiments indicated that the age of CD51+ SLCs plays a more significant role in determining age-related inhibitory effects. In LC lineage formation, CD51+ SLC had both reduced LC lineage markers and increased myoid cell lineage markers, suggesting an age-related lineage shift for SLCs.ConclusionThe results suggest that aging affected both SLC function and their regulatory niche cell, macrophages

Effects of habitat usage on hypoxia avoidance behavior and exposure in reef-dependent marine coastal species

Reef habitat in coastal ecosystems is increasingly being augmented with artificial reefs (ARs) and is simultaneously experiencing increasing hypoxia due to eutrophication and climate change. Relatively little is known about the effects of hypoxia on organisms that use complex habitat arrangements and how the presence of highly preferred AR habitat can affect the exposure of organisms to low dissolved oxygen (DO). We performed two laboratory experiments that used video recording of behavioral movement to explore 1) habitat usage and staying duration of individuals continuously exposed to 3, 5, and 7 mg/L dissolved oxygen (DO) in a complex of multiple preferred and avoided habitat types, and 2) the impact of ARs on exposure to different DO concentrations under a series of two-way replicated choice experiments with or without AR placement on the low-oxygen side. Six common reef-dependent species found in the northeastern sea areas of China were used (i.e., rockfish Sebastes schlegelii and Hexagrammos otakii, filefish Thamnaconus modestus, flatfish Pseudopleuronectes yokohamae, sea cucumber Stichopus japonicus, and crab Charybdis japonica). Results showed that lower DO levels decreased the usage of preferred habitats of the sea cucumber and the habitat-generalist filefish but increased the habitat affinity to preferred habitat types for the two habitat-specific rockfishes. Low DO had no effect on the crab’s habitat usage. In the choice experiment, all three fish species avoided 1 mg/L, and the rockfish S. schlegelii continued to avoid the lower DO when given choices involving pairs of 3, 5, and 7 mg/L, while H. otakii and the flatfish showed less avoidance. The availability of ARs affected exposure to low DO for the habitat-preferring rockfishes but was not significant for the flatfish. This study provides information for assessing the ecological effects and potential for adaptation through behavioral movement for key reef-dependent species under the increasing overlap of ARs and hypoxia anticipated in the future