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

Study on overlying strata containing primary fractures migration and spatial-temporal characteristics of water gushing (leaching) caused by mining field disturbance

The super-thick, high-pressure, medium-strong water-rich Luohe Formation aquifer is overlying in the Binchang mining area of Shanxi Province, and the fractures in the overlying rock are developed, it makes the water channel easier to communicate with the aquifer and stope of Luohe Formation, resulting in the increase of water inflow and area in the stope. In order to study the morphological characteristics of water inrush induced by the network of water-conducting channels formed by primary fractures communicating with the aquifer of the thick Luohe Formation under the influence of mining, the solid-flow coupling similar material simulation test was carried out based on the similar simulation physical experiment system of water-sand inrush in overburden rock. The results show that when the working face is advanced to 140 m, the lower strata of the bed separation are broken in advance due to the influence of the primary fractures. The left incomplete bed separation space and the triangular space formed by the right cantilever beam support form the “Z” bed separation space. When the working face is advanced to 160 m, two “Z-type” bed separation spaces are developed in the overlying strata, which are interconnected with the primary fractures and mining-induced fractures to form a water channel network. The form of gushing (leaching) water in the stope changed from ‘ drip-drip and flow-flow-multi-state ’, and the overall gushing (leaching) water volume increased first and then decreased. The water pressure of overlying strata and the advancing distance of the working face show a segmented evolution characteristic of decreasing first and then increasing. The minimum interval and the position of the inflection point of the segmentation increase with the increase of the distance between the monitoring point and the open-off cut. The final water pressure values near the central area of the goaf are greater than the two boundary monitoring points. The analysis results show that the existence of primary fractures promotes the development of water-conducting fracture channel network, accelerates the process of water transport, and induces the formation and development of water gushing (leaching) in the stope. The research results clarify the influence of primary fractures on the distribution characteristics of water conduction channel network and the evolution law of water gushing (leaching) form morphology, and explain the conduction mechanism of thick and high confined aquifer water to stope water inrush

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

Exploration of accessibility of internal pore surface by using rigid nanoparticles as a probe for constructing the integrated nanocomposites

Many mesoporous materials with different morphologies, dimensions, pore sizes and structures have been fabricated and served as carriers to load a wide range of guest species. The high accessibility of pore interiors should be of very significance for efficient loading in the nanocarriers and resultant performance of the formed nanocomposites. In this work, by electrostatic self-assembly, the rigid nanoparticles (NPs) were used as probes to detect the accessibility of internal surface of different pore channels of two typical porous materials, i.e., conventional mesoporous silica nanospheres (MSNs) with uniform hexagonal ordered mesopores and recently created dendritic porous silica NPs (DPSNs) with center-radial porous structure. Interestingly, even 1.6 +/- 0.4 nm of ultrafine Au NPs have an uneven and low density distribution on the internal pore surface of MSNs owing to small tubular pores with only two openings. On the contrary, the rigid NPs with different particle sizes from 1.6 +/- 0.4 nm to 7.8 +/- 1.9 nm can enter DPSNs through open center-radial large pores with 360 degrees diffusion direction, and achieve a high density and well-dispersed loading on the surface of internal pore channels. Besides, based on the size effect, the integrated DPSNs-NH2@Au@Pt nanocomposite with hierarchical spatial distributions of large Au NPs on particle surface and small Pt NPs on both internal pore surface and particle surface were successfully constructed. These results provide an important insight into the accessibility of internal pore surface toward rigid NPs and the smart construction of multifunctional nanocomposites. (C) 2019 Elsevier B.V. All rights reserved

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]