Projected Hybrid Orbitals: A General QM/MM Method

A projected hybrid orbital (PHO) method was described to model the covalent boundary in a hybrid quantum mechanical and molecular mechanical (QM/MM) system. The PHO approach can be used in ab initio wave function theory and in density functional theory with any basis set without introducing system-dependent parameters. In this method, a secondary basis set on the boundary atom is introduced to formulate a set of hybrid atomic orbtials. The primary basis set on the boundary atom used for the QM subsystem is projected onto the secondary basis to yield a representation that provides a good approximation to the electron-withdrawing power of the primary basis set to balance electronic interactions between QM and MM subsystems. The PHO method has been tested on a range of molecules and properties. Comparison with results obtained from QM calculations on the entire system shows that the present PHO method is a robust and balanced QM/MM scheme that preserves the structural and electronic properties of the QM region

Rh-Catalyzed Asymmetric Hydrogenation of Cyclic α‑Dehydroamino Ketones

Catalyzed by a rhodium complex of P-stereogenic diphosphine trichickenfootphos, five-membered cyclic α-dehydroamino ketones bearing endocyclic acyl and endocyclic vinyl groups were hydrogenated to give chiral α-amino ketones with quantitative conversions and excellent enantioselectivities

Sample characteristics.

‡<p>Number of children differs across sample characteristics due to missing values.</p

Mean IQ and 2009 school performance by blood concentrations of lead in preschool children.

<p>Mean IQ and 2009 school performance by blood concentrations of lead in preschool children.</p

Impact of blood concentrations of lead on IQ and school performance in Chinese preschool children (n = 1341).

*<p><b>p<.05,</b></p>**<p><b>p<.01.</b></p><p>Model 1: Adjusting for age at blood lead test, sex, blood iron, school, father's education, mother's education, father's occupation and smoking.</p><p>Model 2: Adjusting covariates in model 1 plus PIQ.</p

FIQ, VIQ, and PIQ test scores by blood lead concentration (µg/dl) with estimated 95% confidence bands.

<p>Note: The dotted line's <i>y</i>-intercept is at the mean IQ test score.</p

Pearson correlations between blood lead concentrations and IQ and school performance.

*<p>p<.05;</p>**<p>p<.01,</p>***<p>p<.001.</p>‡<p>Number of children differs across sample characteristics due to missing values.</p

The morphological changes in control cells and cells treated with differentiation inducers (400×).

<p>The ATRA-treated group showed few embryoid bodies (EB) on day 2 and the EB number increased during days 4–10. Large numbers of SSC-like cells were observed on day 10. The Am80-treated group showed EB around 4 days, and SSC-like cells were observed on day 10. The E2-treated group showed EB at day 4 and the EB number increased during days 4–8. SSC-like cells were observed around day 10;</p

Efficient Catalytic Activity of Ti₃C₂T_<i>x</i> MXene for Polyester Synthesis

Polyethylene terephthalate (PET) is one of the most widely used polymers for beverage packaging and fibers, with antimony-based catalysts currently dominating its synthesis. However, concerns about potential safety hazards associated with antimony leaching necessitate the development of environmentally benign catalysts free from heavy metals. In this work, we report the first-time utilization of Ti3C2Tx MXene as a polycondensation catalyst of PET. The intrinsic viscosity of Ti3C2Tx MXene-catalyzed PET could reach 0.78 dL/g within 2.1 h, which demonstrated a superior catalytic efficiency compared to antimony trioxide (Sb2O3). Moreover, Ti3C2Tx MXene exhibited a satisfactory performance not only in PET synthesis but also in the production of polypropylene terephthalate (PPT) and polybutylene terephthalate (PBT), thereby confirming its universality in polyester catalysis. The catalytic activity of Ti3C2Tx MXene in polycondensation reactions was attributed to the presence of strong Lewis acid sites, as supported by surface examinations and computational studies. Notably, Ti3C2Tx MXene-catalyzed PET exhibited satisfied crystallizability, as confirmed by the short crystallization half-time of only 6.9 s at 185 °C, signifying a high crystallization rate. This work highlights the potential applications of this thriving 2D material in polyester catalysis and, more importantly, provides a new perspective for the exploration and design of efficient and environmentally friendly catalyst/nucleation agents for polyester synthesis

Selection of the Inducer for the Differentiation of Chicken Embryonic Stem Cells into Male Germ Cells <i>In Vitro</i>

<div><p>Several inducers have been used to differentiate embryonic stem cells (ESCs) into male germ cells but the induction process has been inefficient. To solve the problem of low efficiency of inducer for ESCs differentiation into male germ cells, all-trans retinoic acid (ATRA), Am80(the retinoic acid receptor agonist), and estradiol (E2) was used to induce ESCs to differentiate into male germ cells <i>in vitro</i>. ESCs were cultured in media containing ATRA, Am80, or E2 respectively which can differentiate ESCs into a germ cell lineage. In process of ATRA and Am80 induction Group, germ cell-like cells can be observed in 10 days; but have no in E2 induction Group. The marker genes of germ cell: <i>Dazl</i>, <i>Stra8</i>, <i>C-kit</i>, <i>Cvh</i>, <i>integrinα6</i>, and <i>integrinβ1</i> all showed a significant up-regulation in the expression level. The ATRA-induction group showed high expression of <i>C-kit</i> and <i>Cvh</i> around 4 days, and integrinα6 and integrinβ1 were activated on day 10, respectively, while the E2-,Am80- induction group showed a high expression of <i>C-kit</i> as early as 4 days immunocytochemistry results shown that, <i>integrinα6</i> and <i>integrinβ1</i> could be detected in the ATRA-, Am80-, and E2-induction group, Positive clones in the ATRA group were greater in number than those in the other two groups. we conclued that ATRA, Am80, and E2 can promote the expression of the corresponding genes of germ cells, and had different effect on the differentiation of ESCs into male germ cells. ATRA was the most effective inducer of germ cell differentiation.</p></div