High Glass Transition Temperature Fluorinated Polymers Based on Transfer Learning with Small Experimental Data.

Machine learning can be used to predict the properties of polymers and explore vast chemical spaces. However, the limited number of available experimental datasets hinders the enhancement of the predictive performance of a model. This study proposes a machine learning approach that leverages transfer learning and ensemble modeling to efficiently predict the glass transition temperature (Tg) of fluorinated polymers and guide the design of high Tg copolymers. Initially, the quantum machine 9 (QM9) dataset is employed for model pretraining, thus providing robust molecular representations for the subsequent fine-tuning of a specialized copolymer dataset. Ensemble modeling is used to further enhance prediction robustness and reliability, effectively addressing the problems owing to the limited and unevenly distributed nature of the copolymer dataset. Finally, a fine-tuned ensemble model is used to navigate a vast chemical space comprising 61 monomers and identify promising candidates for high Tg fluorinated polymers. The model predicts 247 entries capable of achieving a Tg over 390 K, of which 14 are experimentally validated. This study demonstrates the potential of machine learning in material design and discovery, highlighting the effectiveness of transfer learning and ensemble modeling strategies for overcoming the challenges posed by small datasets in complex copolymer systems.

Mg3Si3(MoO6)2 as a High-Performance Cathode Active Material for Magnesium-Ion Batteries.

The natural abundance of magnesium together with its high volumetric energy capacity and less-dendritic anodes makes Mg-ion batteries an appealing alternative to the widely used Li-ion batteries. However, Mg cathode materials under current investigation suffer from various shortcomings such as low operation voltage and high energy barrier for ion migration, resulting in poor battery performance. Here, we propose a garnet-type intercalation cathode active material, Mg3Si3(MoO6)2, for high-performance Mg-ion batteries. Through first-principles density functional theory calculations, it is demonstrated that Mg3Si3(MoO6)2 possesses a high average discharge voltage (2.35 V vs Mg/Mg2+), a low ion migration barrier (∼0.2 eV), and a minimal volume change (∼4%) concurrently, which comprises excellent intercalation cathode chemistry. The small energy barrier for ion migration is shown to arise from the favorable change in the Mg coordination along the migration route within the garnet host. These findings present an additional direction to develop competent Mg-ion batteries for future energy storage applications.

Effect of morphological change of copper-oxide fillers on the performance of solid polymer electrolytes for lithium-metal polymer batteries.

Solid polymer electrolytes (SPEs) for Li-metal polymer batteries are prepared, in which poly(ethylene oxide) (PEO), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), and copper-oxide fillers are formulated. Their structural and electrochemical properties are analyzed when the morphology of the copper-oxide fillers has been modulated to spherical or dendritic structure. The ionic conductivity obtained by electrochemical impedance spectroscopy (EIS) has been increased to 1.007 × 10-4 S cm-1 at 30 °C and 1.368 × 10-3 S cm-1 at 60 °C, as the 5 wt% dendritic fillers have been added to the SPEs. This ionic conductivity value is 1.3 times higher than that of 5 wt% spherical filler-contained SPEs. The analyses of differential scanning calorimetry (DSC) and X-ray diffraction (XRD) indicate that the increase of ionic conductivity is due to the remarkable decrease of crystallinity upon the addition of copper-oxide filler into PEO matrix of SPEs. The fabricated SPEs with the dendritic copper-oxide fillers present a total ionic transference number of 0.99 and a lithium-ion transference number of 0.38. More importantly, it presents a stable potential window of 2.0-4.8 V at 25 °C and high thermal stability up to 300 °C. The specific discharge capacity of the prepared cell with the dendritic filler-contained SPEs is measured to be 51 mA h g-1 and 125 mA h g-1 under 0.1 current-rate (C-rate) at 25 °C and 60 °C, respectively. In this study, the ionic conductivity and the electrochemical performance of the PEO-based polymer electrolyte have been evaluated when morphologically different copper-oxide fillers have been incorporated into the PEO matrix. We have also confirmed the safety and the flexibility of the prepared solid polymer electrolytes when they are used in flexible lithium-metal polymer batteries (LMPBs).

Theoretical Analysis for Proton Conductivity at σ3 Tilt Grain Boundary of Barium Cerate.

We theoretically analyzed proton conductivity at the σ3 tilt grain boundary (GB) of barium cerate using density functional theory. Two types of positively charged defects, a proton and an oxygen vacancy, were segregated at the GB with segregation energies in the range of -0.36(-) -0.52 and -0.17(-)-0.30 eV, respectively. Segregated defects at the GB built up an electrostatic potential of 0.41 V at 600 K. The segregated proton at the GB required energy barriers in the range of 0.66-0.86 eV in order to migrate across the GB. Based on the electrostatic potential and energy barriers, proton conductivities in bulk, and at the GB of barium cerate, were calculated and compared with experimental values.

Initial surface reaction of di-lsopropylaminosilane on a fully hydroxyl-terminated Si (001) surface.

We studied the interaction of di-isopropylaminosilane (SiH3N(C3H7)2, DIPAS) molecules with a fully hydroxyl-terminated Si (001) surface for SiO2 thin-film growth by using density functional theory. The amino group consisting of DIPAS was chosen in order to obtain a high adsorption energy because its lone-pair electrons in the N atom would help in the adsorption of DIPAS. The absolute value of the adsorption energy (0.67 eV) of DIPAS was higher than its reaction energy barrier of 0.38 eV. Thus, DIPAS could react with the surface without desorption. The reaction between DIPAS and the surface produced a silyl group (-SiH3) as a primary product and di-isopropylamine (NH(C3H7)2, DIPA) as a by-product. A second DIPAS, which was adsorbed near the pre-adsorbed DIPAS or -SiH3 with DIPA, required higher reaction energy barriers of 3.91 or 1.92 eV, respectively, because of its interaction with the first DIPAS or DIPA. However, when the second DIPAS was adsorbed near -SiH3 without DIPA, a low reaction energy barrier of 0.42 eV was required, indicating a negligible effect of -SiH3 on the second DIPAS reaction. Therefore, to obtain a highly dense Si layer, DIPA must desorb from the surface. DIPA requires a relatively high desorption energy of 0.40 eV because the lone-pair electrons in the N atom of DIPA also enhance its adsorption on the surface. The high desorption energy could reduce the process window of atomic layer deposition.

Associations between organochlorine pesticides and vitamin D deficiency in the U.S. population.

BACKGROUND: Recently low dose organochlorine (OC) pesticides have been strongly linked to various chronic diseases including diabetes and cardiovascular diseases. Both field and animal studies have suggested a possibility that persistent lipophilic chemicals like OC pesticides can cause vitamin D deficiency, but there have been no human studies of exposure to any chemical as a possible cause of vitamin D deficiency. This study was performed to examine if serum concentrations of OC pesticides were associated with serum concentrations of 25-hydroxyvitamin D (25(OH)D) in the U.S. general population. METHODOLOGY/PRINCIPAL FINDINGS: Cross-sectional associations of serum OC pesticides with serum 25(OH)D were investigated in 1,275 subjects aged ≥20 in the National Health and Nutrition Examination Survey (NHANES), 2003-2004. We selected 7 OC pesticides detectable in ≥80% of participants. Among the 7 OC pesticides, p,p'-DDT (ß = -0.022, P<0.01), p,p'-DDE (ß = -0.018, P = 0.04), and ß-hexachlorocyclohexane (ß = -0.022, P = 0.02) showed significant inverse associations with serum 25(OH)D levels. When study subjects were stratified by age, race, and the presence of various chronic diseases, p,p'-DDT showed consistent inverse associations in all subgroups, although stronger associations tended to be observed among subjects with old age, white race, or chronic diseases. CONCLUSION/SIGNIFICANCE: The current study suggests that the background exposure to some OC pesticides leads to vitamin D deficiency in human. Considering the importance of vitamin D deficiency in the development of chronic diseases, chemical exposure as a possible cause of vitamin D deficiency should be evaluated in prospective and experimental studies.

Prevalence of Diabetes Mellitus and Prediabetes in Dalseong-gun, Daegu City, Korea.

BACKGROUND: The aim of the present study was to determine the population-based prevalence of diabetes mellitus (DM) and prediabetes in a rural district of Daegu City, Korea. METHODS: Between August and November 2003, a community-based health survey of adults aged 20 years and older was performed in the rural district of Dalseong-gun in Daegu City. A total of 1,806 of all eligible individuals agreed to participate. Fasting plasma glucose was measured in all participants. Two hour oral glucose tolerance was measured in the 1,773 participants for whom there was neither an established diagnosis of DM nor evidence of DM according to fasting glucose levels. The prevalence of DM and prediabetes was determined according to the 2003 criteria of the American Diabetes Association. Subjects with prediabetes were classified into one of three categories of glucose intolerance: isolated impaired fasting glucose (IFG); isolated impaired glucose tolerance (IGT); or combined IFG and IGT. RESULTS: The prevalence of DM was 12.2%. The highest prevalence rates were observed in subjects in their seventies. A total of 34.7% of all subjects who were assigned a diagnosis of DM in the present study had not been diagnosed previously. The prevalence of prediabetes was 22.7%. The highest prevalence rates were observed in subjects in their fifties. CONCLUSION: The present study identified prevalence rates of 12.2% for DM (age-standardized prevalence rate [ASR], 6.8%), and 22.7% for prediabetes (ASR 18.5%). These results emphasize the need for community health promotion strategies to prevent or delay the onset of DM in individuals with prediabetes.

[Factors affecting re-smoking in male workers].

OBJECTIVES: This study was performed to examine the factors affecting re-smoking in male workers. METHODS: A self-administrated questionnaire survey was conducted during April 2003 to examine the smoking state of 1,154 employees of a company that launched a smoking cessation campaign in 1998. Five hundred and eighty seven persons, who had stopped smoking for at least one week, were selected as the final study subjects. This study collected data on smoking cessation success or failure for 6 months, and looked at the factors having an effect on resmoking within this period. This study employed the Health Belief Model as its theoretical basis. RESULTS: The re-smoking rate of the 587 study subjects who had stopped smoking for at least one week was 44.8% within the 6 month period. In a simple analysis, the resmoking rates were higher in workers with a low age, on day and night shifts, blue collar, of a low rank, where this was their second attempt at smoking cessation and for those with a shorter job duration (p<0.05). Of the cues to action variables in the Heath Belief Model, re-smoking was significantly related with the perceived susceptibility factor, economic advantages of smoking cessation among the perceived benefits factor, the degree of cessation trial's barrier of the perceived barriers factor, smoking symptom experience, recognition of the degree of harmfulness of environmental tobacco smoke and the existence of chronic disease due to smoking (p<0.05). In the multiple logistic regression analysis for re-smoking, the significant variables were age, perceived susceptibility for disease, economic advantages due to smoking cessation, the perceived barrier for smoking cessation, recognition on the degree of harmfulness of environmental tobacco smoke, the existence of chronic disease due to smoking and the number of attempts at smoking cessation (p<0.05). CONCLUSION: From the result of this study, for an effective smoking ban policy within the work place, health education that improves the knowledge of the adverse health effects of smoking and the harmfulness of environmental tobacco smoke will be required, as well as counter plans to reduce the barriers for smoking cessation.

[The association between serum GGT level within normal range and risk factors of cardiovascular diseases].

OBJECTIVES: We conducted this study to examine the association between serum GGT levels within the normal range and the risk factors of cardiovascular diseases METHODS: We examined the cross-sectional association between serum GGT and the systolic and diastolic blood pressure, fasting blood glucose, total cholesterol, triglyceride, high density lipoprotein cholesterol (HDL-cholesterol), and uric acid among 975 subjects that participated in the health examination of a university hospital located in Daegu city. All the patients' GGT levels were within the normal range. RESULTS: After adjustment were made for age, body mass index (BMI), smoking status, drinking frequency, exercise frequency and coffee intake, the serum GGT level was positively associated with fasting blood glucose (p < 0.01), total cholesterol (p < 0.01), and triglyceride (p < 0.01) in men, and it was positively associated with fasting blood glucose (p < 0.01), total cholesterol (p < 0.05), triglyceride (p < 0.01), and uric acid (p < 0.01) in women. The associations were not significantly different depending on the status of alcohol drinking or obesity, except for the associations of serum GGT with diastolic blood pressure (P for interaction = 0.04) and uric acid (P for interaction = 0.04) between the lean and obese subjects. CONCLUSIONS: Serum GGT levels within the normal range were positively associated with fasting blood glucose, triglyceride and uric acid in most subgroups irrespective of the drinking or obesity status. These results suggest that GGT has important clinical implications as being more than just a marker of alcohol consumption and hepatobiliary disease.

Is serum gamma-glutamyltransferase inversely associated with serum antioxidants as a marker of oxidative stress?

A series of studies in black and white women and men have suggested that serum gamma-glutamyltransferase (GGT) within its normal range might be an early marker of oxidative stress. If serum GGT is a marker of oxidative stress, it might have important implications both clinically and epidemiologically because measurement of serum GGT is easy, reliable, and not expensive. We examined the cross-sectional association between deciles of serum GGT and concentrations of serum antioxidants among 9083 adult participants in the third U.S. National Health and Nutrition Examination Survey. After adjustment for race, sex, age, and total cholesterol, serum concentration of GGT across all deciles was inversely associated with serum concentrations of alpha-carotene, beta-carotene, beta-cryptoxanthin, zeaxanthin/lutein, lycopene, and vitamin C (p for trend <.01, respectively). Vitamin E was not associated with serum GGT. All these associations were not materially different after additional adjustment for total energy intake, body mass index, smoking status, smoking amount, alcohol intake, and exercise. These associations were similarly observed among most subgroups. In conclusion, the current and previous studies strongly suggest that serum GGT level within its normal range may be an early marker of oxidative stress.