Search

Stable isotope labelled p-methoxybenzoic acid is an important intermediate in the synthesis of stable isotope labelled preservative, anti-microbial, anti-fungal, spices, and other internal standard reagentsspices, drugs and other compounds. A new procedure for the synthesis of the ［13C］/D labelled p-methoxybenzoic acid has been developed in this paper. The stable isotope ［13C］/D labelled p-methoxybenzoic acid was synthesized from ethyl paraben and ［13C］/D labelled iodomethane (13CH3I or CD3I) under alkaline conditions via two steps. In this paper, the optimal reaction temperature, molar ratio, and reaction time were obtained by single factor experiment. The optimal reaction conditions were obtained as follows, the reaction temperature was 80 ℃, the molar ratio of ［13C］/D labelled iodomethane to ethyl paraben was 1.15∶1, the reaction time was 6 h. In the optimization conditions, the yield of ［13C］ labelled p-methoxybenzoic acid was 91.12%, and the utilization of 13CH3I was 79.32%. The melting point of product was 186.5~187.8 ℃. The product analyses were made with LC-MS, the chemical purity was 99.1%, and the isotopic abundance was 99.0 atom%13C. The qualitative analysis of product was confirmed by 1H NMR. By the same technological conditions, the stable isotope ［D］ labelled p-methoxybenzoic acid was synthesized from ethyl paraben and ［D］ labelled iodomethane (CD3I). The yield of ［D］ labelled p-methoxybenzoic acid was 90.49%, and the utilization of CD3I was 78.70%, and the melting point of product was 186.3~188.1 ℃. The product analyses were made with LC-MS, the chemical purity was 99.0%, and the isotopic abundance was 98.1 atom%D. The qualitative analysis of product was confirmed by 1H NMR.

A novel synthesis method of protocatechuic acid-(13COOH) was designed. 3,4-dimethoxy bromobenzene as raw material, Grignard reagent was prepared by Grignard reaction, then passed through the 13C labeled 13CO2 gas, the intermediate 3,4-dimethoxy benzoic acid-(13COOH) was prepared. The crude product was obtained viademethylation with BBr3, which was decolorizing by activated carbon. Protocatechuic acid-(13COOH) was obtained by cooling crystallization. Synthesis route had the advantages of simple operation, short process flow, less side product, the yield was more than 45%, 13C labeled isotope abundance was not diluted. The product was characterized by HPLC, MS, 1H NMR and 13C NMR, the chemical purity was more than 99%, 13C enrichment was more than 98%. As an important tracer, it can provide a basis for medical and chemical research.

To obtain solid inclusions in LF refining process, the influence of silicon content in steel on compositions of inclusions during LF refining were investigated in Al-killed steel. Influence of sili...

To obtain solid Al2O3 or MgO·Al2O3 inclusions in ladle furnace (LF) refining process and achieve ultra-low total oxygen content in steel through subsequent Ruhrstahl Heraeus degassing, the effects of ferrosilicon alloy, Si content of steel, and slag basicity on the compositions of inclusions during LF refining were investigated in Al-killed steel. Al2O3 inclusions could be transformed into CaO–Al2O3–MgO–CaS inclusions after adding ferrosilicon alloy in the LF refining process as this alloy contains some CaSi alloy impurities. The addition of all ferrosilicon alloys required for the steel in the tapping process could eliminate the influence of Ca in ferrosilicon alloy on the compositions of inclusions. Si in liquid steel had a significant influence on the compositions of inclusions during LF refining when CaO–Al2O3–SiO2–MgO slag with high basicity of 7.0 was used. This was because [Ca] produced by the reaction of CaO and [Al] could be consumed more readily by SiO2 in Si-free steel than in Si-containing steel, which was confirmed by the difference of total calcium content between Si-free and Si-containing steels. As a result, Al2O3 and MgO·Al2O3 inclusions were retained in Si-free steel, whereas calcium aluminate inclusions were found in Si-containing steel. For CaO–Al2O3–SiO2–MgO slag with low basicity of 2.8, Al2O3 and MgO·Al2O3 inclusions were obtained after LF refining in Si-containing steel when all ferrosilicon alloys required for the steel were added in the tapping process. This was because the reaction of CaO and [Al] was weak, and residual [Ca] in the steel could be rapidly consumed by SiO2 in low-basicity slag owing to the low activity of CaO and high activity of SiO2, leading to a low total calcium content of 0.0003% in Si-containing steel.

Additional file 1. Detailed search strategy in each database.

In this paper, we consider AdS$_{3}$ with Compère-Song-Strominger (CSS) boundary conditions, under which the dual field theory is warped conformal field theory (WCFT), featuring a Virasoro-Kac-Moody algebra. We provide a holographic dual picture of the single interval entanglement entropy in WCFT in the bulk AdS$_{3}$. We explicitly show that the bulk object captures the entanglement entropy in WCFT is a massive spinning particle's worldline that anchored on the boundary of the interval. Given the mass and spin of the particle as functions of quantum numbers of the twist operator in WCFT, the on-shell worldline action will match the entanglement entropy in WCFT.

Since 1950, more than 620 potato cultivars have been released from Chinese breeding programs, some of which have similar genetic background and phenotype. In this study, 16 parental cultivars widely used in breeding were used to screen 138 simple sequence repeat (SSR) markers. Out of 138 SSR markers, 20 were polymorphic that were used to analyze the genetic diversity of 217 potato cultivars grown in China. In total, 249 alleles were detected with these 20 markers and 244 of them (97.99%) showed polymorphism. The number of alleles ranged from 7 to 22 with an average of 12.45 alleles per primer and polymorphic information content (PIC) ranged from 0.64–0.93 with an average of 0.83. Fragment sizes varied from 80 to 380 bp. Based on PIC values and the clarity of PCR amplification bands, 11 SSR markers were selected and able to differentiate all of the 217 cultivars. The estimated similarity using these polymorphic SSR markers between the cultivars ranged from 0.63 to 0.99, indicating a narrow genetic base. Fingerprinting and genetic diversity analysis in this study provides useful information for the protection of intellectual property, as well as the exploration and utilization of these potato cultivars.

A scheme to a complex-valued acquisition of the Fourier transform imaging was proposed. The main idea is to project the real and the imaginary parts of a diffraction field to intensity distributions respectively. The whole procedure was algorithm independent and needs no a priori knowledge of an arbitrary objet. An example was demonstrated with a numerical modeling and its results., Welcome Comments

This paper introduces the national industry standard "DL-476-92 the application layer protocol for real time data communications in electric power system ", issued by the Ministry of Energy, People's Republic of China, in April of 1992. The authors are members of the protocol development working group. >

A high speed inductorless limiting amplifier (LA) in an optical communication receiver with the working speed up to 20 Gb/s is presented. The LA includes an input matching network, a four-stage 3rd order amplifier core, an output buffer for the test and a DC offset cancellation (DCOC). It uses the active interleaving feedback technique both to broaden the bandwidth and achieve the flatness response. Based on our careful analysis of the DCOC and stability, an error amplifier is added to the DCOC loop in order to keep the offset voltage reasonable. Fabricated in the 65 nm CMOS technology, the LA only occupies an area of 0.45 × 0.25 mm2 (without PAD). The measurement results show that the LA achieves a differential voltage gain of 37 dB, and a 3-dB bandwidth of 16.5 GHz. Up to 26.5 GHz, the Sdd11 and Sdd22 are less than −16 dB and −9 dB. The chip excluding buffer is supplied by 1.2 V VDD and draws a current of 50 mA.