Studies toward the synthesis of hyperevolutin A : nitrile oxide-allene cycloaddition approach

This thesis described research conducted on the synthesis of hyperevolutin A—an antitumor antibiotic. An introduction related to the structural and synthetic aspects of polyisoprenylated phloroglucinol natural products is given in section 1. The study investigated an unprecedented intramolecular nitrile oxide-allene approach to a hindered bicyclo[3.3.1] ring system as well as the β,β\u27-tricarbonyl unit. The research results are summarized in section 2 and described in two separate sections—acyclic model and cyclic model. The acyclic model showed that the β,γ-double bond of the allene is more reactive and this result is attributed to thermodynamic preference. In the cyclic model, the α,β-double bond is more reactive as a result of reversed thermodynamic preference. A functionalized core of hyperevolution A was prepared from 2-methylcyclohexanone in 12 steps in 6% overall yield. All experiments related to this research are summarized in section 3

The Difference between Plasmon Excitations in Chemically Heterogeneous Gold and Silver Atomic Clusters

Weak doping can broaden, shift, and quench plasmon peaks in nanoparticles, but the mechanistic intricacies of the diverse responses to doping remain unclear. In this study, we used the time-dependent density functional theory (TD-DFT) to compute the excitation properties of transition-metal Pd- or Pt-doped gold and silver atomic arrays and investigate the evolution characteristics and response mechanisms of their plasmon peaks. The results demonstrated that the Pd or Pt doping of the off-centered 10 × 2 atomic arrays broadened or shifted the plasmon peaks to varying degrees. In particular, for Pd-doped 10 × 2 Au atomic arrays, the broadened plasmon peak significantly blueshifted, whereas a slight red shift was observed for Pt-doped arrays. For the 10 × 2 Ag atomic arrays, Pd doping caused almost no shift in the plasmon peak, whereas Pt doping caused a substantial red shift in the broadened plasmon peak. The analysis revealed that the diversity in these doping responses was related to the energy positions of the d electrons in the gold and silver atomic clusters and the positions of the doping atomic orbitals in the energy bands. The introduction of doping atoms altered the symmetry and gap size of the occupied and unoccupied orbitals, so multiple modes of single-particle transitions were involved in the excitation. An electron transfer analysis indicated a close correlation between excitation energy and the electron transfer of doping atoms. Finally, the differences in the symmetrically centered 11 × 2 doped atomic array were discussed using electron transfer analysis to validate the reliability of this analytical method. These findings elucidate the microscopic mechanisms of the evolution of plasmon peaks in doped atomic clusters and provide new insights into the rational control and application of plasmons in low-dimensional nanostructures

Transparent Flexible IGZO Thin Film Transistors Fabricated at Room Temperature

Flexible and fully transparent thin film transistors (TFT) were fabricated via room temperature processes. The fabricated TFT on the PEN exhibited excellent performance, including a saturation mobility (μsat) of 7.9 cm2/V·s, an Ion/Ioff ratio of 4.58 × 106, a subthreshold swing (SS) of 0.248 V/dec, a transparency of 87.8% at 550 nm, as well as relatively good stability under negative bias stress (NBS) and bending stress, which shows great potential in smart, portable flexible display, and wearable device applications

Pyrene-based blue emitters with aggregation-induced emission features for high-performance organic light-emitting diodes

© 2019 The Royal Society of Chemistry. Pyrene is a representative aggregation-caused quenching (ACQ) chromophore. Herein, by introducing tetraphenylethylene or triphenylethylene with a typical aggregation-induced emission (AIE) characteristic at pyrene's 2,7-positions, we have succeeded in converting it into AIE luminogens (AIEgens). The new compounds, namely Py-TPE and Py-TriPE, exhibit strong sky-blue emission

Associations of prenatal exposure to per- and polyfluoroalkyl substances and fetal sex hormones in the Guangxi Zhuang Birth Cohort Study: Greater effect of long-chain PFAS

Fetal sex hormone homeostasis disruption could lead to reproductive and developmental abnormalities. However, previous studies have reported inconsistent findings regarding the association of maternal per- and polyfluoroalkyl substances (PFAS) exposure with fetal sex hormone levels. A total of 277 mother-infant pairs from the Guangxi Zhuang Birth Cohort Study between 2015 and 2019 were selected. We quantified nine PFAS in maternal serum in early pregnancy, and detected three sex hormones, namely, estradiol (E2), progesterone (P4) and testosterone (TT), in cord blood. The generalized linear model (GLM) and Bayesian kernel machine regression (BKMR) model were used for single- and multiple-exposure analyses, respectively. In the GLM, there was no significant association between an individual PFAS and any hormone level or the E2/TT ratio, but a negative association between perfluorododecanoic acid (PFDoA) exposure and P4 levels in female infants was observed after stratification by sex. In the BKMR, a mixture of nine PFAS was positively associated with E2 levels and the E2/TT ratio, with the same main contributors, i.e., perfluoroundecanoic acid (PFUnA). And PFAS mixtures were not associated with P4 or TT levels. After stratification by infant sex, positive associations of PFAS mixtures with E2 levels and the E2/TT ratio were observed only in male infants, with the same main contributors, i.e., PFUnA. There was a positive association between PFAS mixtures and P4 levels in male infants, in which PFUnA was the main contributor; but a reverse association between PFAS mixtures and P4 levels in female infants, in which PFDoA was the main contributor. This study suggested that prenatal exposure to PFAS mixtures is associated with fetal sex hormones, and long-chain PFAS may play an important role in this association. Furthermore, sex differences in the association of maternal PFAS exposure with E2 and P4 levels need additional attention

Associations between Serum Aflatoxin-B1 and Anemia in Pregnant Women: Evidence from Guangxi Zhuang Birth Cohort in China

Aflatoxin B1 (AFB1) is a common toxic mycotoxin and is detectable in pregnant women. Animal studies have revealed that AFB1 caused the lysis of erythrocytes and a decrease in hemoglobin. We conducted a prospective cohort study in Guangxi, China, in order to evaluate the association between AFB1 exposure and anemia in pregnant women during the entire pregnancy. A total of 616 pregnant women from the Guangxi Zhuang Birth Cohort were included in the study. Serum AFB1-albumin (AFB1-ALB) adduct levels were measured. The effect of AFB1-ALB adducts on hemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) were analyzed by using multivariable linear regression. The risks of anemia from AFB1-ALB adduct exposure were assessed by multivariable logistic regression. We found that the AFB1-ALB adduct was significantly associated with a decrease in Hb (β = −4.99, 95% CI: −8.42, −1.30), MCV (β = −4.58, 95% CI: −7.23, −1.94), MCH (β = −1.86, 95% CI: −2.87, −0.85), and MCHC (β = −5.23, 95% CI: −8.28, −2.17) in the first trimester with the third tertile of AFB1-ALB adducts when compared with the first tertile. Furthermore, the third tertile of the AFB1-ALB adduct significantly increased the risk of anemia by 2.90 times than compared to the first tertile in the first trimester (OR = 3.90, 95% CI: 1.67, 9.14). A significant positive does–response relationship existed between AFB1-ALB adduct levels and anemia risk (Ptrend = 0.001). When dividing anemia types, we only found that the third tertile of AFB1-ALB adduct increased the risk of microcytic hypochromic anemia (MHA) in the first trimester (OR = 14.37, 95% CI: 3.08, 67.02) and second trimester (OR = 4.75, 95% CI: 1.96, 11.51). These findings demonstrate the correlation between maternal AFB1 exposure during early pregnancy and risk of anemia, especially MHA, and during different trimesters in Southern China. More efforts should be made to diminish AFB1 exposure for pregnant women