Cobalt(I)-Catalyzed [2+2] and [3+2] Cycloaddition Reactions between Alkylidenecyclopropanes and Alkynes

Alkylidenecyclopropanes (ACPs) are highly-strained but thermally-stable structures that can undergo a multitude of different reactions with the assistance of transition metal catalysts, especially cycloaddition reactions toward the synthesis of carbocycles and heterocycles. However, the majority of reported reactions utilize harsh conditions such as high temperature or other high-energy compounds. ACP reactivity has seldom been explored under cationic cobalt(I)-catalyzed systems. Here, we report two novel cobalt(I)-catalyzed cycloaddition reactions between ACPs and alkynes: (i) an enantioselective [2+2] cycloaddition that yields uncommon spiro[2.3]hex-4-ene motif up to 80% yield and up to 96% ee; and (ii) a [3+2] cycloaddition that yields alkylidenecyclopent-1-ene structures between 20-60% yield. Both reactions are performed under ambient conditions.U.S. National Institute of Health (R01 GM108762 to TVR)U.S. National Science Foundation (CHE-1362095 and CHE-1900141 to TVR)No embargoAcademic Major: Chemistr

Language reorganization patterns in global aphasia–evidence from fNIRS

BackgroundExploring the brain reorganization patterns associated with language recovery would promote the treatment of global aphasia. While functional near-infrared spectroscopy (fNIRS) has been widely used in the study of speech and language impairment, its application in the field of global aphasia is still limited.AimsWe aimed to identify cortical activation patterns of patients with global aphasia during naming and repetition tasks.Methods and proceduresWe recruited patients with post-stroke aphasia from the Department of Rehabilitation Medicine at Huashan Hospital. These individuals were diagnosed with global aphasia without cognitive impairments, as assessed by speech-language pathology evaluations. Age- and sex-matched healthy controls were recruited from the greater Shanghai area. During fNIRS measurement, patients and healthy controls completed the picture-naming and phrase repetition task. Cortical activation patterns on each of these language tasks were then compared between groups.Outcomes and resultsA total of nine patients with global aphasia and 14 healthy controls were included in this study. Compared with the healthy subjects, patients with global aphasia showed increased activation in the left Broca's area, middle temporal gyrus (MTG), superior temporal gyrus (STG), and pre-motor and supplementary motor cortex (SMA) (p < 0.05) in the picture-naming task. Furthermore, the latency of the oxyhemoglobin (HbO) concentration in the left supramarginal gyrus (SMG) region had a strong negative correlation with their score of the naming task (p < 0.01). In the phrase repetition task, decreased activation was detected in the left SMA and SMG (p < 0.05) of patients relative to controls.ConclusionThe left SMG plays a critical role in the language function of patients with global aphasia, especially in their abilities to name and repeat. fNIRS is a promising approach to revealing the changes in brain activities in patients with aphasia, and we believe it will contribute to a deeper understanding of the neurological mechanisms and the establishment of a novel treatment approach for global aphasia

Far-field transient absorption nanoscopy with sub-50 nm optical super-resolution

Nanoscopic imaging or characterizing is the mainstay of the development of advanced materials. Despite great progress in electronic and atomic force microscopies, label-free and far-field characterization of materials with deep sub- wavelength spatial resolution has long been highly desired. Herein, we demonstrate far-field super-resolution transient absorption (TA) imaging of two-dimensional material with a spatial resolution of sub-50 nm. By introducing a donut- shaped blue saturation laser, we effectively suppress the TA transition driven by near-infrared (NIR) pump–probe photons, and push the NIR-TA microscopy to sub-diffraction-limited resolution. Specifically, we demonstrate that our method can image the individual nano-grains in graphene with lateral resolution down to 36 nm. Further, we perform super-resolution TA imaging of nano-wrinkles in monolayer graphene, and the measured results are very consistent with the characterization by an atomic force microscope. This direct far-field optical nanoscopy holds great promise to achieve sub-20 nm spatial resolution and a few tens of femtoseconds temporal resolution upon further improvement and represents a paradigm shift in a broad range of hard and soft nanomaterial characterization

Ultrafast and reversible electrochemical lithiation of InAs nanowires observed by in-situ transmission electron microscopy

The electrochemical lithiation/delithiation processes of InAs nanowires (NWs) are studied by in-situ transmission electron microscopy. Our results indicate that InAs NWs have a fast lithiation speed of 275 nm/s and a high lithium ion (Li-ion) diffusion coefficient of 2.49 x 10(-8) cm(2)/s at room temperature. Upon lithiation, the Li-ion insertion firstly results in severe lattice distortions of InAs NWs, and the formation of Li3As and LixIn through the conversion and alloying processes take place on further lithiation. A small volume expansion of 157% is observed in full lithiation and is attributed to the naturally formed surface oxide layer. During the delithiation process, volume contraction and the dealloying of LixIn take place. Induced by the alloying and dealloying of LixIn, the dark and bright strips along the basal plane of InAs NWs appear and disappear alternately during the lithiation-delithiation cycling. Our results provide important insights into the lithiation/delithiation mechanism of III-V group nanomaterials and are envisaged to be helpful for designing lithium ion battery anode materials with fast lithiation speed, small volume expansion and reversible lithiation/delithiation processes. (C) 2015 Elsevier Ltd. All rights reserved.MOST of the China [2012CB932702, 2012CB932701]; NSF of China [11374022, 61371001, 11304003, 61321001]; Foundation for the Author of National Excellent Doctoral Dissertation of China [201241]; Specialized Research Fund for the Doctoral Program of Higher Education of China [20130001110030]SCI(E)[email protected]; [email protected]; [email protected]

Deep Learning Structure for Cross-Domain Sentiment Classification Based on Improved Cross Entropy and Weight

Within the sentiment classification field, the convolutional neural network (CNN) and long short-term memory (LSTM) are praised for their classification and prediction performance, but their accuracy, loss rate, and time are not ideal. To this purpose, a deep learning structure combining the improved cross entropy and weight for word is proposed for solving cross-domain sentiment classification, which focuses on achieving better text sentiment classification by optimizing and improving recurrent neural network (RNN) and CNN. Firstly, we use the idea of hinge loss function (hinge loss) and the triplet loss function (triplet loss) to improve the cross entropy loss. The improved cross entropy loss function is combined with the CNN model and LSTM network which are tested in the two classification problems. Then, the LSTM binary-optimize (LSTM-BO) model and CNN binary-optimize (CNN-BO) model are proposed, which are more effective in fitting the predicted errors and preventing overfitting. Finally, considering the characteristics of the processing text of the recurrent neural network, the influence of input words for the final classification is analysed, which can obtain the importance of each word to the classification results. The experiment results show that within the same time, the proposed weight-recurrent neural network (W-RNN) model gives higher weight to words with stronger emotional tendency to reduce the loss of emotional information, which improves the accuracy of classification