Oxidative C-H Bond Activation:Study on DDQ-Induced Intramolecular Cyclization Reactions and Application to the Formal Synthesis of Neopeltolide

2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) has been found to be an excellent reagent for oxidatively activating benzylic C-H bonds, and the in-situ generated oxocarbenium ions can be captured by nucleophiles appended in the molecules. A variety of aromatic methyl ethers with different substituents are shown to be reactive with DDQ, and common protecting groups are well tolerated. The enol acetate group is the most reliable and productive nucleophile compared with other candidates and provides the 2,6-disubstituted tetrahydropyrone product as exclusively the cis isomer. This method has been successfully applied to the macrocyclic systems. The valuable macrocyclic oxocarbenium ions are readily formed when treating the substrates with DDQ. The reactions are generally slower than those of acyclic substrates but the yields are almost unaffected. The ring size has no influence on the diastereoselectivity of cyclization.A convergent formal synthesis of natural product neopeltolide was accomplished from three building blocks by utilizing the DDQ mediated cyclization reaction as the key transformation. A novel intramolecular hydrosilylation-Tamao oxidation reaction is employed to synthesize the precursor for the key step. This approach to the natural product has minimized the involvement of protecting groups and conveniently provided an opportunity to access the natural product analogues through double bond functionalizations

Large-scale BN tunnel barriers for graphene spintronics

We have fabricated graphene spin-valve devices utilizing scalable materials made from chemical vapor deposition (CVD). Both the spin-transporting graphene and the tunnel barrier material are CVD-grown. The tunnel barrier is realized by h-BN, used either as a monolayer or bilayer and placed over the graphene. Spin transport experiments were performed using ferromagnetic contacts deposited onto the barrier. We find that spin injection is still greatly suppressed in devices with a monolayer tunneling barrier due to resistance mismatch. This is, however, not the case for devices with bilayer barriers. For those devices, a spin relaxation time of 260 ps intrinsic to the CVD graphene material is deduced. This time scale is comparable to those reported for exfoliated graphene, suggesting that this CVD approach is promising for spintronic applications which require scalable materials.Comment: 13 pages, 3 figure

Natural channel protein inserts and functions in a completely artificial, solid-supported bilayer membrane

Reconstitution of membrane proteins in artificial membrane systems creates a platform for exploring their potential for pharmacological or biotechnological applications. Previously, we demonstrated amphiphilic block copolymers as promising building blocks for artificial membranes with long-term stability and tailorable structural parameters. However, the insertion of membrane proteins has not previously been realized in a large-area, stable, and solid-supported artificial membrane. Here, we show the first, preliminary model of a channel membrane protein that is functionally incorporated in a completely artificial polymer, tethered, solid-supported bilayer membrane (TSSBM). Unprecedented ionic transport characteristics that differ from previous results on protein insertion into planar, free-standing membranes, are identified. Our findings mark a change in understanding protein insertion and ion flow within natural channel proteins when inserted in an artificial TSSBM, thus holding great potential for numerous applications such as drug screening, trace analyzing, and biosensing

Estimation of Source and Receiver Positions, Room Geometry and Reflection Coefficients From a Single Room Impulse Response

We propose an algorithm to estimate source and receiver positions, room geometry and reflection coefficients from a single room impulse response simultaneously. It is based on a symmetry analysis of the room impulse response. The proposed method utilizes the times of arrivals of the direct path, first order reflections and second order reflections. The proposed method is robust to erroneous pulses and non-specular reflections. It can be applied to any room with parallel walls as long as the required arrival times of reflections are available. In contrast to the state-of-art method, we do not restrict the location of source and receiver

Effects of Soft Golf on Physical Fitness of Children Aged 4 to 5 Years

Playing golf is good for health. Previous studies found that golf training can improve performance such as muscle strength, endurance, balance, and agility. Constitution is the important foundation of national and social development, and children are the key period of constitution development. At present, there are few studies on the influence of golf on children\u27s physical fitness. This study explored the influence of 16-week soft golf exercise intervention on the physical health of 4–5-year-old children. Sixty children aged 4-5 years old were recruited from a kindergarten school in Shanghai, China with means of age at 4.56±0.54 and height at 112.72±3.96. Participants were randomly assigned into experimental group and control group. The physical fitness data were collected before and after the intervention. The intervention lasted 16 weeks of soft golf training with twice a week and 45 minutes each time. The control group did not do any training. The results showed that: (1) there were no significant differences between the experimental group and the control group in terms of lower limb strength and coordination ability. After intervention, Participants in the experimental group performed significantly better than those in the control group. (2) There were no significant differences in upper limb strength, endurance, and balance among participants between the experimental group and the control group. After intervention, Participants in the experimental group and the control group improved in physical fitness at varying degrees when compared with the pre-test, however the improvements were not statistically significant. This study showed that after 16 weeks of soft golf intervention, participants in the experimental group and the control group had different degrees of improvement in physical fitness test indicators. Especially in lower limb strength and coordination ability test indicators, participants in the experimental group performed significantly higher than those in the control group. It is suggested that the impact of soft golf on children\u27s physical fitness was positive. In China, research on golf and children\u27s physical fitness is still in its infancy. Soft golf retains the characteristics of traditional golf, and the development conditions are more convenient, which provide objective conditions for campus golf. The exercise effect of soft golf on physical fitness among different participants should be further explored in the future

Wind pattern analysis applied to Tokyo 2020 Olympic Games (II)

Meteorologists refer to repeating weather conditions as a weather pattern. A weather pattern is characterised by repeating values of weather variables, such as atmospheric pressure, cloud coverage, air temperature, wind speed and direction, etc

A Complex Event Processing-Based Online Shopping User Risk Identification System

Online shopping is an important part of the development of the Internet and plays a critical role in the current and future economy. However, there are many risks in the trading process. In order to reduce the hidden risks, it is necessary to study the method of risk identification. This paper proposes user risk identification method of online shopping system based on Complex Event Process (CEP). In this paper, we use the Esper as the CEP engine and the risk behavior patterns are defined as the event pattern language. Firstly, the CEP system captures event streams by analyzing data streams in real-time. Secondly, the captured event streams are sent to the CEP's engine. Finally, the Esper intelligently analyzes user's online shopping risk behaviors in real-time according to the event pattern languages. User risk identification effectively guarantees the fund and account security of the shopping users