New insight on the origin of the unusual acidity of Meldrum's acid from ab initio and combined QM/MM simulation study.

Ab initio molecular orbital and combined QM/MM Monte Carlo simulations have been carried out to investigate the origin of the unusually high acidity of Meldrum's acid. Traditionally, the high acidity of Meldrum's acid relative to that of methyl malonate has been attributed to an additive effect due to the presence of two E esters in the dilactone system. However, the present study reveals that there is significant nonadditive effect that also makes major contributions. This results from preferential stabilization of the enolate anion over that of Meldrum's acid due to anomeric stereoelectronic interactions. To investigate solvent effects on the acidity in aqueous solution, the relative acidities of Z and E conformers of methyl acetate have been determined in combined ab initio QM/MM simulations. There is significant solvent effect on the conformational equilibria for both the neutral ester and its enolate anion in water, leading to stabilization of the E stereoisomer. However, the computed solvent effect of 4.4 kcal/mol in favor of the E isomer of methyl acetate is largely offset by the favorable solvation of 3.4 kcal/mol for the E conformer of the enolate anion. This leads to an enhanced acidity of 3.4 kcal/mol for the (E)-methyl acetate in water over the Z conformer. In Meldrum's acid, it is the preferential stabilization of the enolate anion due to anomeric effects coupled with the intrinsically higher acidity of the E conformation of ester that is responsible for its high acidity.     

Comparative effects of gamma irradiation and phosphine fumigation on the quality of white ginseng

The hygienic, physicochemical, and organoleptic qualities of white ginseng were monitored during 6 months under accelerated conditions (40°C, 90% r.h.) by observing its microbial populations, disinfestation, and some quality attributes following either gamma irradiation at 2.5–10 kGy or commercial phosphine (PH₃) fumigation. In a comparative study, both treatments were found to be effective for disinfecting the stored samples. Phosphine showed no appreciable decontaminating effects on microorganisms contaminated including coliforms, while 5 kGy irradiation was sufficient to control all microorganisms related to the quality of the packed samples. Irradiation at 5 kGy caused negligible changes in physicochemical attributes of the samples, such as ginsenosides, amino acids, fatty acids, and organoleptic properties, whereas phosphine fumigation was found detrimental to sensory flavor (P<0.01). Quality deterioration occurred in the commercially-packed samples was in the following order: the control, 10 kGy-, phosphine-, and 2.5–5 kGy-treated samples. Accordingly, irradiation at <5 kGy was found to be an effective alternative to phosphine fumigation for white ginseng.     

Application of QPLEXTM biomarkers in cognitively normal individuals across a broad age range and diverse regions with cerebral amyloid deposition

The deposition of beta-amyloid (Aβ) in the brain precedes the onset of symptoms such as cognitive impairment in Alzheimer’s disease (AD); therefore, the early detection of Aβ accumulation is crucial. We previously reported the applicability of the QPLEX^TM Alz plus assay kit for the prescreening of Aβ accumulation. Here, we tested the specific application of the kit in a large cohort of cognitively normal (CN) individuals of varying ages for the early detection of Aβ accumulation. We included a total of 221 CN participants with or without brain Aβ. The QPLEX^TM biomarkers were characterized based on age groups (1^st–3^rd tertile) and across various brain regions with cerebral amyloid deposition. The 3^rd tertile group (>65 years) was found to be the most suitable age group for the application of our assay kit. Receiver operating characteristic curve analysis showed that the area under the curve (AUC, discrimination power) was 0.878 with 69.7% sensitivity and 98.4% specificity in the 3^rd tertile group. Additionally, specific correlations between biomarkers and cerebral amyloid deposition in four different brain regions revealed an overall correlation with general amyloid deposition, consistent with previous findings. Furthermore, the combinational panel with plasma Aβ1–42 levels maximized the discrimination efficiency and achieved an AUC of 0.921 with 95.7% sensitivity and 67.3% specificity. Thus, we suggest that the QPLEX^TM Alz plus assay is useful for prescreening brain Aβ levels in CN individuals, especially those aged >65 years, to prevent disease progression via the early detection of disease initiation.Subject terms: Alzheimer''s disease, Neural ageing, ELISA     

Stereocontrolled enantioselective addition of diethylzinc to aldehydes using new chiral aminoalcohols

The new chiral β-aminoalcohols of indolinylmethanols ( 1 ) and their reduced derivatives ( 2 ) were synthesized from (S)-indoline-2-carboxylic acid. Both (R) and (S) enantiomers of the optically active secondary alcohols have been successfully obtained in high enantiomeric excess from the stereoselective addition of diethylzinc to the aldehydes catalyzed by the chiral aminoalcohols ( 1 and 2 ). The sense of the asymmetric induction and the degrees of enantioselectivities turned out to be highly dependent on the structure of the catalysts: The presence of the catalyst 1 afforded the (S)-configuration of the corresponding alcohols; on the other hand, the presence of 2 afforded the (R)-configuration of the alcohols in high enantiomeric selectivity.     

Portrait Segmentation Using Ensemble of Heterogeneous Deep-Learning Models

Image segmentation plays a central role in a broad range of applications, such as medical image analysis, autonomous vehicles, video surveillance and augmented reality. Portrait segmentation, which is a subset of semantic image segmentation, is widely used as a preprocessing step in multiple applications such as security systems, entertainment applications, video conferences, etc. A substantial amount of deep learning-based portrait segmentation approaches have been developed, since the performance and accuracy of semantic image segmentation have improved significantly due to the recent introduction of deep learning technology. However, these approaches are limited to a single portrait segmentation model. In this paper, we propose a novel approach using an ensemble method by combining multiple heterogeneous deep-learning based portrait segmentation models to improve the segmentation performance. The Two-Models ensemble and Three-Models ensemble, using a simple soft voting method and weighted soft voting method, were experimented. Intersection over Union (IoU) metric, IoU standard deviation and false prediction rate were used to evaluate the performance. Cost efficiency was calculated to analyze the efficiency of segmentation. The experiment results show that the proposed ensemble approach can perform with higher accuracy and lower errors than single deep-learning-based portrait segmentation models. The results also show that the ensemble of deep-learning models typically increases the use of memory and computing power, although it also shows that the ensemble of deep-learning models can perform more efficiently than a single model with higher accuracy using less memory and less computing power.     

Ambient xenon sampling using an Ag/ZSM-5 zeolite

Journal of Radioanalytical and Nuclear Chemistry - An ambient xenon sampling system using Ag/ZSM-5 was designed, and its performance was tested. The xenon collection efficiency of the system was...     

Molecular dynamics study on the field effect ion transport in carbon nanotube

We investigated potassium ion transport in the (5, 5) carbon nanotube by using classical molecular dynamics simulations under applying external force fields. This can be applied to nanoscale ionic-field-effect devices. As the applying external force field increases, the potassium ions rapidly go through the nanochannel. Under the low external force fields, the thermal fluctuation of the nanochannel affected on the tunneling of the potassium ions, whereas the effects of the thermal fluctuation were negligible under the high external force fields.     

Factors affecting product distributions in ethylene/styrene copolymerization by (aryloxo)(cyclopentadienyl)titanium complexes‐MAO catalyst systems

Ethylene/styrene copolymerizations using Cp′TiCl₂(O‐2,6‐ⁱPr₂C₆H₃) [Cp′ = Cp* (C₅Me₅, 1 ), 1,2,4‐Me₃C₅H₂ ( 2 ), tert‐BuC₅H₄ ( 3 )]‐MAO catalyst systems were explored under various conditions. Complexes 2 and 3 exhibited both high catalytic activities (activity: 504–6810 kg‐polymer/mol‐Ti h) and efficient styrene incorporations at 25, 40°C (ethylene 6 atm), affording relatively high molecular weight poly (ethylene‐co‐styrene)s with unimodal molecular weight distributions as well as with uniform styrene distributions (M_w = 6.12–13.6 × 10⁴, M_w/M_n = 1.50–1.71, styrene 31.7–51.9 mol %). By‐productions of syndiotactic polystyrene (SPS) were observed, when the copolymerizations by 1 – 3 ‐MAO catalyst systems were performed at 55, 70 °C (ethylene 6 atm, SPS 9.0–68.9 wt %); the ratios of the copolymer/SPS were affected by the polymerization temperature, the [styrene]/[ethylene] feed molar ratios in the reaction mixture, and by both the cyclopentadienyl fragment (Cp′) and anionic ancillary donor ligand (L) in Cp′TiCl₂(L) (L = Cl, O‐2,6‐ⁱPr₂C₆H₃ or N=C^tBu₂) employed. Co‐presence of the catalytically‐active species for both the copolymerization and the homopolymerization was thus suggested even in the presence of ethylene; the ratios were influenced by various factors (catalyst precursors, temperature, styrene/ethylene feed molar ratio, etc.). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4162–4174, 2008     

Genkwalathins A and B,new lathyrane-type diterpenes from Daphne genkwa

Screening for new natural anti-neuroinflammatory compounds was performed with the traditional folk medicine Genkwa Flos, which potently inhibited nitric oxide (NO) production by LPS-activated microglial BV-2 cells. Two new lathyrane-type diterpenes, genkwalathins A (1) and B (2), and 14 known daphnane-type diterpenes (3–16) were isolated. The lathyrane-type diterpenes were isolated for the first time from the Thymelaeaceae family in this study. Compounds 1 and 2 moderately inhibited LPS-induced NO production in BV-2 cells without affecting cell viability, while six daphnane-type diterpenes (3, 4, 6, 7, 9 and 10) potently reduced NO production with IC₅₀ values less than 1 μM, although they did display weak cytotoxicity. A structure–activity relationship study on the daphnane-type diterpenes indicated that the stereochemistry at C-19, the benzoate group at C-20, and the epoxide moiety could be important for their anti-neuroinflammatory effects.     

Inactivation of Enterobacter sakazakii of dehydrated infant formula by gamma-irradiation

Enterobacter sakazakii has been implicated as a causal organism in a severe form of neonatal meningitis, with reported mortality rates of 20%. The population at greatest risk is immunocompromised infants of any age. Dried infant formula has been identified as a potential source of the organism in both outbreaks and sporadic cases. The objective of this study was to investigate theirradiation effect of the inactivation on E. sakazakii (ATCC 29544) of a dehydrated infant formula. The D₁₀-values were 0.22–0.27 and 0.76 kGy for broth and dehydrated infant formula, respectively. The irradiation at 5.0 kGy was able to completely eliminate the E. sakazakii inoculated at 8.0 to 9.0 log CFU g⁻¹ onto a dehydrated infant formula. There was no regrowth for all samples during the time they were stored at 10 °C for 6 h after rehydration. The present results indicated that a gamma-irradiation could potentially be used to inactivate E. sakazakii in a dehydrated powdered infant formula.