Characterization of (H2O)n- clusters using model potential approaches

(H2O)n- clusters have attracted considerable interest since their discovery. Experimentally, three kinds of isomers of (H2O)n- have been identified, but the relationship between the cluster size and the distribution of the excess electron is unknown. The pathways for conversion of the surface- to cavity-bound electron are also controversial. In this thesis, molecular dynamics simulations are applied using a (H2O)n- model introduced by the Jordan group. It is found that for (H2O)6−, the tweezers structure rapidly evolves to the more stable AA structure, however for book structure the energy barrier is much higher and formation of the AA isomer is not observed on the picosecond time scale

Stereocontrolled Cyanohydrin Ether Synthesis through Chiral Brønsted Acid-Mediated Vinyl Ether Hydrocyanation

Vinyl ethers can be protonated to generate oxocarbenium ions that react with Me₃SiCN to form cyanohydrin alkyl ethers. Reactions that form racemic products proceed efficiently upon conversion of the vinyl ether to an α-chloro ether prior to cyanide addition in a pathway that proceeds through Brønsted acid-mediated chloride ionization. Enantiomerically enriched products can be accessed by directly protonating the vinyl ether with a chiral Brønsted acid to form a chiral ion pair. Me₃SiCN acts as the nucleophile and PhOH serves as a stoichiometric proton source in a rare example of asymmetric bimolecular nucleophilic addition into an oxocarbenium ion. Computational studies have provided a model for the interaction between the catalyst and the oxocarbenium ion

Establishing the Ground State of the Disjoint Diradical Tetramethyleneethane with Quantum Monte Carlo

The nature of the electronic ground state of the tetramethyleneethane (TME) diradical has proven to be a challenge for both experiment and theory. Through the use of quantum Monte Carlo (QMC) methods and multireference perturbation theory, we demonstrate that the lowest singlet state of TME is energetically lower than the lowest triplet state at all values of the torsional angle between the allyl subunits. Moreover, we find that the maximum in the potential energy curve for the singlet state occurs at a torsional angle near 45°, in contrast to previous calculations that placed the planar structure of the singlet state as the highest in energy. We also show that the CASPT2 method when used with a sufficiently large reference space and a sufficiently flexible basis set gives potential energy curves very close to those from the QMC calculations. Our calculations have converged the singlet–triplet gap of TME as a function of methodology and basis set. These results provide insight into the level of theory required to properly model diradicals, in particular disjoint diradicals, and provide guidelines for future studies on more complicated diradical systems

Novel Process Methods for the Whole Cottonseed : Effect on the Digestibility, Productivity, Fat Profile, and Milk Gossypol Levels in Lactating Dairy Cows

In this study, we aimed to determine the effect of mixed-process methods on the ruminal degradability of whole cottonseed (WCS) both in situ and in vitro, and the effect on the production performance of dairy cows. Eight WCS process methods were tested on the ruminal digestibility, including crush-alkali 1 (CA1), crush-alkali 2 (CA2), crush-alkali 3 (CA3), alkali 1-crush (A1C), alkali 2-crush (A2C), alkali 3-crush (A3C), crush-only (CO), and non-processed. Alkali 1, 2, and 3 indicate the supplementation of alkali to WCS at the dose of 4% on dry matter (DM) base as followed: 4% NaOH, 2% NaOH + 2% CaO, and 2% NaOH + 2% CaCl2 alkaline, respectively. Among all treatments, CA2 showed the highest WCS ruminal degradation in situ and the highest intestinal digestibility of WCS in vitro. Furthermore, an animal experiment was conducted for 60 days on 30 Holstein dairy cows, using a diet without WCS (CON group), a diet containing 8% non-processed WCS (NP group), and a diet containing 8% CA2-treated WCS (CA2 group). The results indicated that the dry matter intake, 4% fat-corrected milk production, milk protein, milk fat, and content of short-chain saturated fatty acid of milk in the CA2 group were significantly higher (P < 0.05) than CON group. Furthermore, DMI, the CLA was significantly greater (P < 0.05) in the CA2 group than the other groups. Additionally, the free gossypol concentration in serum or milk was under safety level in the three groups. Overall, crush and alkalization (NaOH: CaO = 1:1) treatment could improve the utilization of WCS in dairy farms

Unraveling the Anomalous Solvatochromic Response of the Formate Ion Vibrational Spectrum: An Infrared, Ar-Tagging Study of the HCO₂^¯, DCO₂^¯, and HCO₂^¯·H₂O Ions

Reductive activation offers an attractive synthetic route for conversion of CO₂ to transportable fuels, a process that often involves creation of the formate ion as an intermediate. We carry out an Ar-tagging infrared spectroscopic study of isolated HCO₂^¯ and its first hydrate, HCO₂^¯·H₂O, and analyze the resulting band patterns with electronic structure and vibrationally anharmonic calculations. Strong vibronic interactions and intramolecular mode couplings are identified that are responsible for the deceptively complex solvation behavior of this familiar ion. In particular, the CH stretch fundamental is found to be anomalously low in energy in the isolated ion and to dramatically blue shift (by hundreds of cm^–1) upon solvation. These two effects are traced to the large dependence of the electronic wave function on the CH bond length, reminiscent of the classic curve-crossings that dominate the dissociation behavior of neutral salt molecules

Improvement of atropine on esophagogastric junction observation during sedative esophagogastroduodenoscopy

<div><p>Background and study aims</p><p>Although sedation esophagogastroduodenoscopy (EGD) is now widely used, previous research has reported that sedation during EGD exhibits a negative effect on esophagogastric junction (EGJ) exposure. Atropine might improve EGJ exposure, as noted in clinical practice. The aim of this study was to examine whether sedation had a negative effect on EGJ observation in the Chinese population, and whether atropine had some ability to act as an antidote to this unexpected secondary effect of sedation.</p><p>Patients and methods</p><p>In this cross-sectional study, subjects were divided into the following three groups according to the methods of EGD examination: the non-sedation group, the propofol-fentanyl combined sedation group and the combined sedation with atropine administration group. The EGJ observation was assessed by a key photograph taken with the endoscopic camera 1 cm from the EGJ, which was rated on the following four-degree scale: excellent (score = 4), good (score = 3), fair (score = 2) and poor (score = 1).</p><p>Results</p><p>The EGJ exposure was better in the sedation group administered atropine (score = 2.64±1.05) than in the sedation group (score = 1.99±1.08, P<0.05) but not as good as in the non-sedation group (score = 3.24±1.12, P<0.05). Reduced detection of EGJ diseases in the sedation group was also found, compared to the non-sedation group (P<0.05). Only the use of atropine (OR = 2.381, 95%CI: 1.297–4.371, P = 0.005) was independently associated with excellent observation of the EGJ during sedation EGD.</p><p>Conclusions</p><p>Combined propofol-fentanyl sedation reduces the extent of exposure of the EGJ during EGD and reduces the detection of EGJ diseases. The application of atropine in the sedation endoscopy examination helped to achieve better EGJ observation, but still cannot achieve an equal extent of exposure compared to non-sedation EGD.</p></div

Improvement of atropine on esophagogastric junction observation during sedative esophagogastroduodenoscopy - Fig 1

<p>The esophagogastric junction exposure extent scale <b>(a).</b> Excellent (100% of the EGJ, score = 4) <b>(b).</b> Good (100% > EGJ ≥ 50%, score = 3) <b>(c).</b> Fair (50% > EGJ, score = 2) <b>(d).</b> Poor (EGJ not visualized, score = 1). White lines indicate the observation region.</p

Observed esophagogastric junction region exposure grade and score.

<p>Observed esophagogastric junction region exposure grade and score.</p

Baseline characteristics of subjects.

<p>Baseline characteristics of subjects.</p

Endoscopic findings during EGD.

<p>Endoscopic findings during EGD.</p