Poly[[aqua­(μ2-oxalato)(μ2-2-oxido­pyridinium-3-carboxylato)holmium(III)] monohydrate]

In the title complex, {[Ho(C2O4)(C6H4NO3)(H2O)]·(H2O)}n, the HoIII ion is coordinated by three O atoms from two 2-oxidopyridinium-3-carboxylate ligands, four O atoms from two oxalate ligands and one water mol­ecule in a distorted bicapped trigonal-prismatic geometry. The 2-oxidopyridin­ium-3-carboxylate and oxalate ligands link the HoIII ions into a layer in (100). These layers are further connected by inter­molecular O—H⋯O hydrogen bonds involving the coordinated water mol­ecules to assemble a three-dimensional supra­molecular network. The uncoordin­ated water mol­ecule is involved in N—H⋯O and O—H⋯O hydrogen bonds within the layer

2-(1,3-Dithian-2-yl­idene)-1-phenyl­butane-1,3-dione

The title compound, C13H12O2S2, belonging to the group of dioxoketene cyclic S,S-acetals, was prepared from the corresponding dione in high yield. In the structure, the C=O and C=C bonds are not coplanar, with O=C—C=C torsion angles of −36.8 (4) and −21.0 (4)°. The dithian ring has a twisted conformation

A Comparison of Solid Electrolyte Interphase Formation and Evolution on Highly Oriented Pyrolytic and Disordered Graphite Negative Electrodes in Lithium-Ion Batteries

The presence and stability of solid electrolyte interphase (SEI) on graphitic electrodes is vital to the performance of lithium-ion batteries (LIBs). However, the formation and evolution of SEI remain the least understood area in LIBs due to its dynamic nature, complexity in chemical composition, heterogeneity in morphology, as well as lack of reliable in situ/operando techniques for accurate characterization. In addition, chemical composition and morphology of SEI are not only affected by the choice of electrolyte, but also by the nature of the electrode surface. While introduction of defects into graphitic electrodes has promoted their electrochemical properties, how such structural defects influence SEI formation and evolution remains an open question. Here, utilizing nondestructive operando electrochemical atomic force microscopy (EChem-AFM) the dynamic SEI formation and evolution on a pair of representative graphitic materials with and without defects, namely, highly oriented pyrolytic and disordered graphite electrodes, are systematically monitored and compared. Complementary to the characterization of SEI topographical and mechanical changes during electrochemical cycling by EChem-AFM, chemical analysis and theoretical calculations are conducted to provide mechanistic insights underlying SEI formation and evolution. The results provide guidance to engineer functional SEIs through design of carbon materials with defects for LIBs and beyond

Two-dimensional interlocked pentagonal bilayer ice: how do water molecules form a hydrogen bonding network?

The plethora of ice structures observed both in bulk and under nanoscale confinement reflects the extraordinary ability of water molecules to form diverse forms of hydrogen bonding networks. An ideal hydrogen bonding network of water should satisfy three requirements: (1) four hydrogen bonds connected with every water molecule, (2) nearly linear hydrogen bonds, and (3) tetrahedral configuration for the four hydrogen bonds around an O atom. However, under nanoscale confinement, some of the three requirements have to be unmet, and the selection of the specific requirement(s) leads to different types of hydrogen bonding structures. According to molecular dynamics (MD) simulations for water confined between two smooth hydrophobic walls, we obtain a phase diagram of three two-dimensional (2D) crystalline structures and a bilayer liquid. A new 2D bilayer ice is found and named the interlocked pentagonal bilayer ice (IPBI), because its side view comprises interlocked pentagonal channels. The basic motif in the top view of IPBI is a large hexagon composed of four small pentagons, resembling the top view of a previously reported ‘‘coffin’’ bilayer ice [Johnston, et al., J. Chem. Phys., 2010, 133, 154516]. First-principles optimizations suggest that both bilayer ices are stable. However, there are fundamental differences between the two bilayer structures due to the difference in the selection among the three requirements. The IPBI sacrifices the linearity of hydrogen bonds to retain locally tetrahedral configurations of the hydrogen bonds, whereas the coffin structure does the opposite. The tradeoff between the conditions of an ideal hydrogen bonding network can serve as a generic guidance to understand the rich phase behaviors of nanoconfined water

Two-dimensional interlocked pentagonal bilayer ice: how do water molecules form a hydrogen bonding network?

The plethora of ice structures observed both in bulk and under nanoscale confinement reflects the extraordinary ability of water molecules to form diverse forms of hydrogen bonding networks. An ideal hydrogen bonding network of water should satisfy three requirements: (1) four hydrogen bonds connected with every water molecule, (2) nearly linear hydrogen bonds, and (3) tetrahedral configuration for the four hydrogen bonds around an O atom. However, under nanoscale confinement, some of the three requirements have to be unmet, and the selection of the specific requirement(s) leads to different types of hydrogen bonding structures. According to molecular dynamics (MD) simulations for water confined between two smooth hydrophobic walls, we obtain a phase diagram of three two-dimensional (2D) crystalline structures and a bilayer liquid. A new 2D bilayer ice is found and named the interlocked pentagonal bilayer ice (IPBI), because its side view comprises interlocked pentagonal channels. The basic motif in the top view of IPBI is a large hexagon composed of four small pentagons, resembling the top view of a previously reported ‘‘coffin’’ bilayer ice [Johnston, et al., J. Chem. Phys., 2010, 133, 154516]. First-principles optimizations suggest that both bilayer ices are stable. However, there are fundamental differences between the two bilayer structures due to the difference in the selection among the three requirements. The IPBI sacrifices the linearity of hydrogen bonds to retain locally tetrahedral configurations of the hydrogen bonds, whereas the coffin structure does the opposite. The tradeoff between the conditions of an ideal hydrogen bonding network can serve as a generic guidance to understand the rich phase behaviors of nanoconfined water

A fluorescent probe based on cucurbit[7]uril for the selective recognition of phenylalanine

© 2020 Elsevier B.V. Herein we describe a simple fluorescence quenching method for the selective recognition and determination of the amino acid phenylalanine (Phe). The use of 1H NMR spectroscopy revealed that the alkaloid palmatine (PAL) can encapsulated partially into the cavity of cucurbit[7]uril (Q[7]) in aqueous solution to form a stable 1:1 host−guest inclusion complex. This host-guest complex exhibits fluorescence of moderate intensity. Interestingly, the addition of the Phe results in a dramatic quenching of the fluorescence intensity associated with the inclusion complex. By contrast, the addition of other natural amino acids resulted in no change in the fluorescence. Based on the linear relationship between the fluorescence intensity and the concentration of Phe, the detection of the concentration of Phe in aqueous solution is facile. Thus, a new fluorescence quenching method for the recognition and determination of the Phe has established herein

Genetic testing of sperm donors in China: a survey of current practices

BackgroundThe National Health and Family Planning Commission of China (NHFPCC) issued the “Measures for the Management of Human Sperm Banks,” which was revised in 2003 and is still in effect today. One of the standard guidelines is that potential donors undergo laboratory testing to exclude infectious and genetic diseases and karyotype analysis. However, patient demands for donor genetic testing have also increased, and only karyotype analysis to exclude genetic diseases is not sufficient to meet these demands.ObjectiveTo examine donor genetic screening practices at sperm banks in China and to evaluate the qualifications and skills of genetic counselors at the banks.Materials and methodsAn electronic survey was distributed to twenty-seven sperm banks to examine donor genetic screening practices at sperm banks in China and to evaluate the qualifications and skills of genetic counselors at the banks. Twenty-six human sperm banks responded to a 32-question survey about their current practices related to genetic testing of sperm donors.ResultsThe 26 sperm banks reported that all qualified sperm donors undergo karyotype analysis; 22 banks (84.6%) collected three generations of family history from each qualified sperm donor; 10 (38.5%) reported that they attempted to accommodate special requests from donor semen recipients for particular genetic tests. Only 2 of the 26 (7.7%) sperm banks reported that they performed whole-exome sequencing. At all the sperm banks, consent for genetic testing was obtained as part of the overall contract for sperm donors. Nineteen (73.1%) sperm banks had genetic counselors on their staff, while six (23.1%) had no genetic counselors on their staff but had access to genetic counselors at the hospital. Only one (3.8%) sperm bank had no genetic counselors on their staff or at the hospital.ConclusionsThe need for larger scale genetic testing of donors and recipients and an extensive panel of genetic tests specific to the Chinese population. Additionally, professionally trained geneticists must be employed as genetic counsellors so that the results of genetic tests and their implications can be explained to donors

Mortality and Attrition Rates within the First Year of Antiretroviral Therapy Initiation among People Living with HIV in Guangxi, China: An Observational Cohort Study

Objective. To assess the mortality and attrition rates within the first year of antiretroviral therapy (ART) initiation among people living with human immunodeficiency virus (PLHIV) in rural Guangxi, China. Design. Observational cohort study. Setting. The core treatment indicators and data were collected with standard and essential procedures as per the Free ART Manual guidelines across all the rural health care centers of Guangxi. Participants. 58,115 PLHIV who were under ART were included in the study. Interventions. The data collected included sociodemographic characteristics that consist of age, sex, marital status, route of HIV transmission, CD4 cell count before ART, initial ART regimen, level of ART site, and year of ART initiation. Primary and Secondary Outcome Measures. Mortality and attrition rate following ART initiation. Results. The average mortality rate was 5.94 deaths, and 17.52 attritions per 100 person-years within the first year of ART initiation among PLHIV. The mortality rate was higher among intravenous drug users (Adjusted Hazard Ratio (AHR) 1.27, 95% Confidence Interval (CI) 1.14-1.43), prefecture as a level of ART site (AHR 1.14, 95% CI 1.02-1.28), and county as the level of ART site (AHR 2.12, 95% CI 1.90-2.37). Attrition was higher among intravenous drug users (AHR 1.87, 95% CI 1.75-2.00), the first-line ART containing AZT (AHR 1.09, 95% CI 1.03-1.16), and first-line ART containing LVP/r (AHR 1.34, 95% CI 1.23-1.46). Conclusion. The mortality and attrition rates were both at the highest level in the first year of post-ART; continued improvement in the quality of HIV treatment and care is needed