Ring-Opening Oligomerization Mechanism of a Vanillin-Furfurylamine-Based Benzoxazine and a Mono-Azomethine Derivative.

Exploring the ring-opening polymerization (ROP) mechanism of benzoxazines is a fundamental issue in benzoxazine chemistry. Though some research papers on the topic have been reported, the ROP mechanism of mono-benzoxazines is still elusive. The key point for mechanistic studies is to determine and characterize the structure and formation pathways of the products generated in ROP. In this paper, the ROP of a vanillin-furfurylamine-based benzoxazine and a mono-azomethine derivative is studied with differential scanning calorimetry, fourier transform infrared spectroscopy, nuclear magnetic resonance, and electrospray ionization mass spectrometry, respectively. The results show that the products consist of a range of cationic species, zwitterions, fragments, and series of cyclic and linear oligomers of varying molecular sizes. It is proposed that both mono-benzoxazines undergo thermally activated cationic ring-opening oligomerization via zwitterion intermediates. Upon thermal induction, multi-bond-cleavage takes place to form various zwitterionic intermediates, which react with a monomer, a fragment, or a second zwitterion by several pathways to generate cyclic and linear oligomers.

Application of ultrasound combined with noninvasive prenatal testing in prenatal testing.

BACKGROUND: Both noninvasive prenatal testing (NIPT) and prenatal ultrasound are widely used in clinical settings due to their safety, noninvasiveness, and accuracy, showing high detection rates for fetal chromosomal aneuploidies and structural abnormalities. However, whether the combined application of these two techniques has higher clinical applicability remains to be demonstrated. METHODS: The clinical and laboratory data of 3,050 pregnant women who underwent NIPT were collected. The clinical feasibility and health economics of NIPT were investigated by analyzing the accuracy, postnatal follow-up results, and population applicability of NIPT. In addition, an analysis ultrasonography, NIPT, and karyotyping results were performed to evaluate the combined application of ultrasonography and NIPT in screening fetal chromosomal abnormalities. RESULTS: NIPT could accurately detect trisomies 21, 18, and 13, and was highly sensitive and specific in detecting other autosomal and sex chromosomal aneuploidies. The positive rates of chromosomal abnormalities in the presence of 1 or 2 or more ultrasound markers were 7.5% and 29.2%, respectively, indicating that ultrasonography combined with NIPT should be preferred for the detection of fetal chromosomal abnormalities. CONCLUSIONS: Health economic analysis revealed NIPT to be superior to conventional serologic screening in terms of accuracy and socioeconomics. Ultrasound and NIPT are complementary to each other and the combined techniques can improve the screening ability of fetal chromosomal abnormalities and provide clinicians with more diagnostic information.