High-throughput virtual screening of organic second-order nonlinear optical chromophores within the donor-π-bridge-acceptor framework.

In view of the theoretical importance and huge application potential of second-order nonlinear optical (NLO) materials, it is of great significance to conduct high-throughput virtual screening (HTVS) on a compound library to find candidate NLO chromophores. Under the donor-π-bridge-acceptor structural framework, a virtual compound library (size = 27 090) was constructed by enumeration of structural fragments. The kernel property adopted for optimization is the static first hyperpolarizability (ß0). By combining machine learning and quantum chemical calculations, we have performed an HTVS procedure to sieve NLO chromophores out, and the response mechanism of the selected optimal NLO chromophores was examined. We have found: (a) The multi-layer perceptron/extended connectivity fingerprint combination with 20% selection ratio gives the highest prediction accuracy for the studied systems. (b) The two optimal donors are bis(4-diphenylaminophenyl)aminyl and bis(4-tert-butylphenyl)aminyl; the optimal π-bridges are composed of two thiophenyl, selenophenyl or furanyl units; and the two optimal acceptors are tri-s-triazinyl and 2,3-dicyanopyrazinyl. (c) The no. 1 candidate molecule can exhibit a calculated ß0 equal to 8.55 × 104 a.u. (d) The difference in NLO responses of the optimal 16 molecules comes from the synergistic interaction of ES1, Δµ and f, by employing the two-level model. In addition, the sizable Δµ and f allow the studied optimal molecules to obtain a large NLO response in the meantime keeping a not-too-low excitation energy (retaining good optical transparency in the restricted range of the visible spectrum region). (e) With further modification on the acceptor, the designed DPA-π-TRZ-A' (A' = CN or NO2, π = oligo-thiophenyl or selenophenyl) systems can exhibit a rather large NLO response (maximum ß0 = 3.17 × 105 a.u.), hence should have considerable potential as second-order NLO chromophores. With the above observations, we expect to provide some insight for the research community into the HTVS of organic second-order NLO chromophores.

Chylothorax caused by left atrial myxoma: A rare case report.

BACKGROUND: Myxoma is the most common tumor of the heart that can cause embolism, obstruction, and cardiac failure, but rarely causes chylothorax. We herein report a case of chylothorax caused by left atrial myxoma, which responded to diuretic therapy and was subsequently cured by resecting cardiac myxoma. CASE PRESENTATION: This is a case of a 63-year-old male with symptoms of cardiac insufficiency who was diagnosed with a left atrial myxoma. The patient also had a massive pleural effusion on the right side, which was diagnosed as chylothorax by Sudan III staining and the content of triglyceride. The pleural effusion disappeared and the symptoms of heart failure were relieved after draining the effusion with a fine thoracic drainage tube, but pleural effusion and cardiac insufficiency symptoms relapsed soon. Although diuretic treatment can improve the symptoms and reduced the amount of chylous fluid preoperatively, the chylous pleural effusion was eventually cured by surgical removal of the tumor, and no recurrence of the tumor and chylothorax was found in the 6-month follow-up. CONCLUSIONS: Chylothorax is rare comorbidity of cardiac myxoma. Large myxoma can cause congestive heart failure and lead to disfunction of chylous reflux, resulting in chylothorax, which can be cured by resection of the primary tumor.

Soluble ST2 in Patients with Nonvalvular Atrial Fibrillation and Prediction of Heart Failure.

Atrial fibrillation (AF) is the most common clinically relevant arrhythmia. AF is a strong independent risk factor for the subsequent development of heart failure (HF). HF and AF can interact to perpetuate and exacerbate each other. Soluble ST2 (sST2) is a biomarker of cardiomyocyte stretch that is useful in the diagnosis and prognosis of HF. Its role in the field of AF has not yet been well investigated. We studied the concentration of sST2 in a cohort of 174 subjects (62.1% men; mean age, 65.6 ± 10.3 years [± standard deviation (SD) ]) with nonvalvular AF and 116 age-matched patients with sinus rhythm (SR). Subjects were subdivided into 3 groups: paroxysmal AF, persistent AF, and SR. Plasma sST2 concentrations were measured using an electrochemiluminescence-based immunoassay. The sST2 level was higher in persistent AF patients (P < 0.05) and paroxysmal AF patients (P < 0.05) than in SR patients. No significant difference was found between persistent AF and paroxysmal AF. sST2 was correlated with left atrial diameter (LAD) (r = 0.21; P < 0.01). During a median follow-up time of 6 months, 43 subjects with non-valvular AF in the study had HF. Cox proportional hazard analysis revealed both sST2 and LAD were independent predictors of HF. sST2 concentrations are higher in AF than SR. Plasma sST2 may be a useful biomarker in predicting HF in patients with AF.

Synergistic Effects of 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-Based Derivative and Modified Sepiolite on Flame-Retarded Poly (Ethylene Oxide)-Poly (Butylene Adipate-Co-Terephthalate) Composites.

A 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based derivative (PN-DOPO) combined with aluminium phosphates-coated sepiolite (Sep@AlPO4) was used to improve the flame retardance, thermal stability and mechanical performances of poly (ethylene oxide) (PEO)/poly (butylene adipate-co-terephthalate) (PBAT) blends. The synergistic effects of PN-DOPO and Sep@AlPO4 on flame-retarded PEO/PBAT composites were systematically discussed. Results indicated that introducing 5 wt% Sep@AlPO4 with 10 wt% PN-DOPO into PEO/PBAT achieved a V-1 rating for the UL-94 test and increased the limiting oxygen index value to 23.7%. Moreover, the peak heat release rate (p-HRR), average HRR and total heat release values of PEO/PBAT/PN10%/Sep5% composites decreased by 35.6%, 11.0% and 23.0% compared with those of PEO/PBAT, respectively. Thermogravimetric analysis (TGA) results confirmed that PN-DOPO/Sep@AlPO4 enhanced the initial thermal stability and char yield of PEO/PBAT matrix, and TGA/Fourier transform infrared spectrometry results revealed that the composites exhibited the characteristic absorption peaks of phosphorous-containing groups and an increase in gas-phase volatiles during thermal degradation. The morphological structures of the residues indicated that PN-DOPO and Sep@AlPO4 mixtures produced a more dense and continuous char layer on the composite surface during burning. Rheological behaviour revealed that higher complex viscosity and modulus values of PEO/PBAT/PN-DOPO/Sep@AlPO4 sample could also promote the crosslinking network structure of condensed phases during combustion. Furthermore, the PEO/PBAT/PN-DOPO/Sep@AlPO4 composites exhibited superior elongation at break and flexural performance than the PEO/PBAT system. All results demonstrated that the PEO/PBAT system modified with PN-DOPO/Sep@AlPO4 showed remarkable flame retardance, and improved thermal stability and mechanical properties, indicating its potential application in areas requiring fire safety.

Combining machine learning and quantum chemical calculations for high-throughput virtual screening of thermally activated delayed fluorescence molecular materials: the impact of selection strategy and structural mutations.

In view of the theoretical importance and huge application potential of Thermally Activated Delayed Fluorescence (TADF) materials, it is of great significance to conduct High-Throughput Virtual Screening (HTVS) on compound libraries to find TADF candidate molecules. This research focuses on the computational design of pure organic TADF molecules. By combining machine learning and quantum chemical calculations, using cheminformatics tools, and introducing the concept of selection and mutation from evolutionary theory, we have designed a computational program for HTVS of TADF molecular materials, especially the impact of selection strategy and structural mutations on the results of HTVS was explored. An initial compound library (size = 103) constructed by enumeration of typical donors and acceptors was used to evolve by successively applying selection and 10 different structural mutations. And a group fingerprint similarity (ΔMSPR) index was proposed to account for the similarity between two compound libraries with comparable sizes. Based on the computed data, we have found that the mix of selection and mutations into the evolution map does have great impact on the HTVS results: (a) except the fast mutation Sub2, all the rest of the mutations can effectively concentrate 'good' molecules in a compound library, and hence give large material abundance (typically >0.8) for high mutation generations (n g ≥ 6). (b) The mean energy gap can exhibit a fast convergent trend toward very low values, hence the studied mutations (except Sub2) can cooperate very well with the studied DA substrates to generate optimal molecules, and the group fingerprint similarity can retain high enough values for large n g, which can be associated with the apparent convergence in molecular skeletons as n g increases. (c) The distribution of skeleton frequencies for a specific mutation is generally uneven with one dominant skeleton. The overall numbers of common and generic cores for all mutations are 11 and 7 as n g = 9. Hence, in a sense, the 'optimal' skeletons seem unique and useful in realizing low energy gaps. With these observations and the development of related HTVS software, we expect to provide insight and tools to the research community of HTVS of molecular (TADF) materials.

Synthesis of Aluminum Phosphate-Coated Halloysite Nanotubes: Effects on Morphological, Mechanical, and Rheological Properties of PEO/PBAT Blends.

Polymer blending has been widely used to fabricate polymeric films in the last decade due to its superior properties to a single component. In this study, an aluminum phosphate-coated halloysite nanotube (HNTs@AlPO4) was fabricated using a one-pot heterogeneous precipitation method, organically modified HNTs@AlPO4 (o-HNTs@AlPO4) was used to improve the performance of polyethylene oxide/poly(butylene adipate-co-terephthalate) (PEO/PBAT) blends, and the mechanical and rheological properties of the PEO/PBAT/o-HNTs@AlPO4 films were systematically discussed. According to our results, there is an optimal addition for adequate AlPO4 nanoparticle dispersion and coating on the surface of HNTs, and organic modification could improve the interfacial compatibility of HNTs@AlPO4 and the polymeric matrix. Moreover, o-HNTs@AlPO4 may serve as a compatibilizer between PEO and PBAT, and PEO/PBAT/o-HNTs@AlPO4 films have better mechanical and rheological properties than the PEO/PBAT blends without the o-HNTs@AlPO4 component.

Synergistic Effects of DOPO-Based Derivative and Organo-Montmorillonite on Flame Retardancy, Thermal Stability and Mechanical Properties of Polypropylene.

Polypropylene (PP), as a general thermoplastic polymer, is broadly used in different fields. However, the high flammability, melt dripping and poor mechanical properties of PP are a constraint to the expansion of its applications. In this paper, PP composites containing a combination of a phenethyl-bridged DOPO derivative (PN-DOPO) and organic montmorillonite (OMMT) were prepared via melt blending. The synergistic effects of PN-DOPO and OMMT on the flame retardancy, thermal stability and mechanical properties of PP composites were investigated systematically. The results showed that 20 wt% addition of PN-DOPO with OMMT improved the flame retardancy of PP composites. In particular, the introduction of 17 wt% PN-DOPO and 3 wt% OMMT increased the LOI values of the PP matrix from 17.2% to 23.6%, and the sample reached the V-0 level and reduced the heat release rate and total heat release. TGA indicated that OMMT could improve the thermal stability of the PP/PN-DOPO blends and promote the char residues of PP systems. Rheological behaviour showed a higher storage modulus, loss modulus and complex viscosity of PP/PN-DOPO/OMMT composites, suggesting a more effective network structure. In addition, the tensile strength, flexural properties and impact strength of the PP/PN-DOPO/OMMT composites actually increased for a good dispersion effect. Combined with the char layer analysis, the introduction of OMMT promoted more continuous and compact structural layers containing an aluminium-silicon barrier and phosphorus-containing carbonaceous char in the condensed phase. OMMT can improve the flame retardancy, thermal stability and mechanical properties of PP, and, thus, PN-DOPO/OMMT blends can serve as an efficient synergistic system for flame-retarded PP composites.

Flame-Retardant Performance of Epoxy Resin Composites with SiO2 Nanoparticles and Phenethyl-Bridged DOPO Derivative.

Flame retardancy of epoxy resin (EP) plays a vital role in its applications. When inorganic nanomaterials form inorganic/organic nanocomposites, they exhibit special flame-retardant effects. In this study, EP nanocomposites were prepared by the incorporation of SiO2 nanoparticles and phenethyl-bridged 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivative (DiDOPO), and the synergistic effects of SiO2 nanoparticles and DiDOPO on the flame-retardant performance of EP were discussed. Results indicated that the introduction of only 15 wt % SiO2 and 5 wt % DiDOPO in EP leads to the increase in the limiting oxygen index from 21.8 to 30.2%, and the nanocomposites achieve the UL-94 V-0 rating. Thermogravimetric analysis revealed that char yield increases with the increase in the SiO2 content of the nanocomposites and that an increased amount of thermally stable carbonaceous char is formed. SiO2 nanoparticles can improve the thermal stability and mechanical performance of EP; hence, the nanoparticles can serve as an efficient adjuvant for the DiDOPO/EP flame-retardant system.

Influence of Organo-Sepiolite on the Morphological, Mechanical, and Rheological Properties of PP/ABS Blends.

To improve the poor impact toughness of polypropylene (PP), organo-sepiolite (O-Sep) filled 80/20 (w/w) polypropylene/poly(acrylonitrile-butadiene-styrene) (PP/ABS) nanocomposites were fabricated. The contents of O-Sep were correlated with the morphological, mechanical, and rheological behavior of PP/ABS/O-Sep blends. Scanning electron microscopy (SEM) was applied to study the morphology and thermogravimetric analysis (TGA) was applied to study the thermal stability. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were applied to study the crystallinity. The obtained results show that O-Sep enhanced the dispersion of ABS in the PP matrix and increased the crystallinity of blends. The rheological results show that O-Sep could increase the viscosity, storage modulus, and loss modulus of blends. Moreover, the mechanical behavior shows that O-Sep (at proper content) simultaneously increased the tensile modulus, flexural modulus, and impact strength of PP/ABS/O-Sep blends.