Abstract We report herein on the electrochemical N ‐nitrosation of secondary amines using widely available sodium/potassium nitrite as a nitrosating agent. This approach not only eliminates the need for using a combination of sodium/potassium and a strong acid but also has good functional group tolerance. The reaction is compatible with the late‐stage modification of pharmaceutical compounds and could be conducted in gram scale with a high reaction efficiency. Preliminary mechanistic studies indicate that the N ‐nitrosation occurs via the anodic oxidation of KNO 2 into an NO 2 radical which is then transformed into an NO + cation.
Design method and key technologies of a Ku wide band dual-polarized microstrip antenna with high gain, low back lobe, high port isolation and polarization isolation are given in this paper. To realize Dual-polarization, the antenna is fed by a cross coupling slot. This microstrip antenna consists of a fourlayer structure. To reduce the radiation effect, the feeding lines are placed on the side of ground layer. Compared with conventional microstrip antenna, this improved antenna exhibits higher radiation gain and front-to-back ratio with similar characters on bandwidth, port isolation and polarization isolation. Test results of the improved antenna shows that the gain is above 6.85dBi with 500MHz bandwidth (VSWR <1.5), the isolation of two ports is -53dBc, the polarization isolation is 55dBc, and the front-to-back ratio is 21dBc.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Three new transition metal(ii) phosphonates have been synthesized under mixed-solvothermal conditions. Surface photovoltage and field-induced surface photovoltage spectroscopy of compounds 1 and 2 have been studied. Compound 3 could be used for the sensitive sensing of DMF.
The differences in micro-environment between cancer cells and the normal ones offer the possibility to develop stimuli-responsive drug-delivery systems for overcoming the drawbacks in the clinical use of anticancer drugs, such as paclitaxel, doxorubicin, and etc. Hence, we developed a novel endosomal pH-sensitive paclitaxel (PTX) prodrug micelles based on functionalized poly(ethylene glycol)-poly(ε-caprolactone) (mPEG-PCL) diblock polymer with an acid-cleavable acetal (Ace) linkage (mPEG-PCL-Ace-PTX). The mPEG-PCL-Ace-PTX₅ with a high drug content of 23.5 wt % was self-assembled in phosphate buffer (pH 7.4, 10 mM) into nanosized micelles with an average diameter of 68.5 nm. The in vitro release studies demonstrated that mPEG-PCL-Ace-PTX₅ micelles was highly pH-sensitive, in which 16.8%, 32.8%, and 48.2% of parent free PTX was released from mPEG-PCL-Ace-PTX₅ micelles in 48 h at pH 7.4, 6.0, and 5.0, respectively. Thiazolyl Blue Tetrazolium Bromide (MTT) assays suggested that the pH-sensitive PTX prodrug micelles displayed higher therapeutic efficacy against MCF-7 cells compared with free PTX. Therefore, the PTX prodrug micelles with acetal bond may offer a promising strategy for cancer therapy.
The use of slick-water fracturing fluids has been greatly limited owing to the shortage of water and transportation difficulties in some areas. Serious formation damage occurred in the shale gas reservoirs with low porosity and permeability during the slick-water fracturing with large amounts of water. A fast cross-linking waterless fracturing fluid using the n-hexane/n-octane low-carbon hydrocarbons was prepared in this work. Firstly, a polyphosphate intermediate was synthesized by triethyl phosphate reacting with phosphorus pentoxide, which then reacted with a mixed alcohol of n-butanol, n-octanol, and dodecanol to get the dialkyl phosphate (named as gelling agent). Ferric sulfate, ethylene glycol, sodium citrate, sodium edetate were used to prepare a composite iron-based cross linker with an excellent gelation time and gelation performance, which was composed of 30% ferric sulfate, 10% glycol, 11% trisodium citrate, 9% sodium edetate, and 30% deionized water. By optimizing the ratio of gelling agent to cross linker and the content of gelling agent, an anhydrous fracturing fluid formulation based on n-hexane/n-octane was prepared: n-hexane/n-octyl (mass percent 100%) + gelling agent (1.6%-1.8%)+cross linker (0.6%-0.8%) + gel breaker (0.6%-1.0%).The n-hexane and n-octane fracturing fluids can be used in the formation temperature of 60°C, and 100°C, and the viscosity for the fracturing fluid was 178 and 230 mPa.s under the shear rate of 170 s−1 and shear time for 90 min. The sedimentation velocity of a single ceramsite was 0.2780 cm/min, and the sedimentation velocity of the mixed ceramsite was 0.0022 cm/min, which fully satisfied the fracturing suspension performance. The crushing time of n-hexane and n-octane fracturing fluid was controllable (5–10 h), and the gel breaking effect was excellent (less than 2 mpa.s).
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