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CANAL-TB polymers with defined distributions of methyl and TB groups were prepared, and the isomeric effects on the microstructures and gas separation performance were investigated.

Background This study sought to investigate incidence and risk factors for acute kidney injury (AKI) in hospitalized COVID-19. Methods In this retrospective study, we enrolled 823 COVID-19 patients with at least two evaluations of renal function during hospitalization from four hospitals in Wuhan, China between February 2020 and April 2020. Clinical and laboratory parameters at the time of admission and follow-up data were recorded. Systemic renal tubular dysfunction was evaluated via 24-h urine collections in a subgroup of 55 patients. Results In total, 823 patients were enrolled (50.5% male) with a mean age of 60.9 ± 14.9 years. AKI occurred in 38 (40.9%) ICU cases but only 6 (0.8%) non-ICU cases. Using forward stepwise Cox regression analysis, we found eight independent risk factors for AKI including decreased platelet level, lower albumin level, lower phosphorus level, higher level of lactate dehydrogenase (LDH), procalcitonin, C-reactive protein (CRP), urea, and prothrombin time (PT) on admission. For every 0.1 mmol/L decreases in serum phosphorus level, patients had a 1.34-fold (95% CI 1.14–1.58) increased risk of AKI. Patients with hypophosphatemia were likely to be older and with lower lymphocyte count, lower serum albumin level, lower uric acid, higher LDH, and higher CRP. Furthermore, serum phosphorus level was positively correlated with phosphate tubular maximum per volume of filtrate (TmP/GFR) (Pearson r = 0.66, p

Introduction Acute kidney injury (AKI) in coronavirus disease 2019 (COVID-19) patients is associated with poor prognosis. Early prediction and intervention of AKI are vital for improving clinical outcome of COVID-19 patients. As lack of tools for early AKI detection in COVID-19 patients, this study aimed to validate the USCD-Mayo risk score in predicting hospital-acquired AKI in an extended multi-center COVID-19 cohort. Methods Five hundred seventy-two COVID-19 patients from Wuhan Tongji Hospital Guanggu Branch, Wuhan Leishenshan Hospital, and Wuhan No. Ninth Hospital was enrolled for this study. Patients who developed AKI or reached an outcome of recovery or death during the study period were included. Predictors were evaluated according to data extracted from medical records. Results Of all patients, a total of 44 (8%) developed AKI. The UCSD-Mayo risk score achieved excellent discrimination in predicting AKI with the C-statistic of 0.88 (95%CI: 0.84–0.91). Next, we determined the UCSD-Mayo risk score had good overall performance (Nagelkerke R2 = 0.32) and calibration in our cohort. Further analysis showed that the UCSD-Mayo risk score performed well in subgroups defined by gender, age, and several chronic comorbidities. However, the discrimination of the UCSD-Mayo risk score in ICU patients and patients with mechanical ventilation was not good which might be resulted from different risk factors of these patients. Conclusions We validated the performance of UCSD-Mayo risk score in predicting hospital-acquired AKI in COVID-19 patients was excellent except for patients from ICU or patients with mechanical ventilation.

In this study, three adamantane-containing diamines, i.e. 1,3-bis(4-aminophenyl) adamantane (ADMDA), 1,3-bis(3,5-dimethyl-4-aminophenyl) adamantane (DMADMDA) and 1,3-bis(fluoro-aminophenyl) adamantane (FADMDA), were successfully synthesized by Friedel–Crafts alkylation reactions between 1-adamantanol and acetanilide or its analogues, followed by hydrolysis with aqueous NaOH solution. Three regio-isomers were formed in the case of FADMDA due to the occurrence of both para- and ortho-alkylation (relative to the amino groups). Three series of semi-alicyclic polyimides were subsequently produced through a conventional one-step solution polycondensation between the as-developed diamines and commercial dianhydrides. The properties of the synthesized polyimides were characterized with respect to their thermal, mechanical and optical properties. The adamantane-containing polyimides exhibited significantly high glass transition temperatures (Tg) in the range 285–440 °C, excellent optical transparency (>80% transmittance at 400 nm) and optimal thermal and mechanical properties. The substituents in diamines significantly impacted the properties of the resulting polyimides. Specifically, the polyimides from DMADMDA demonstrated higher d-spacing, higher Tg, lower coefficient of thermal expansion (CTE), better optical properties and inferior tensile properties relative to the ADMDA-derived polymers, which could be attributed to the enhanced chain rigidity and reduced inter- and intra-molecular interactions associated with the two bulky methyl groups. In contrast, the FADMDA-derived polymers exhibited lower d-spacing, lower Tg, higher CTE, higher tensile modulus and lower elongation at break than the ADMDA-based ones, due to the reduced chain linearity regularity caused by the ortho-alkylated isomers, as well as suppressed intramolecular interaction originating from the strongly electron-withdrawing fluorine atoms. The excellent comprehensive properties of the adamantane-containing polyimides render these materials promising candidates for a variety of optical and optoelectronic applications.

A novel dianhydride, 3,3′-di-tert-butyl-2,2′-dimethoxy-[1,1′-binaphthalene]-6,6′,7,7′-tetracarboxylic dianhydride (TNTDA), was prepared via a multi-step process. A model compound made using TNTDA and aniline has a dihedral angle of 75° between the two naphthalimide rings, evidenced by single crystal X-ray diffraction data. High temperature polycondensation of TNTDA with four different diamines afforded four intrinsically microporous polyimides (PIM-PIs). The fractional free volumes (FFV), surface areas, and average inter-chain distances of the polyimides were 0.181–0.214, 379–564 m2 g−1, and 0.635–0.682 nm, respectively. Furthermore, the rigid, bulky, and contorted structures of the PIM-PIs led to the formation of roughly 0.6 nm ultramicropores and roughly 1.2 nm larger micropores. The ultramicropores can improve the gas size-sieving capability of the polyimides, while the larger micropores can facilitate high permeability. Consequently, the TNTDA-based PIM-PIs showed an improved gas separation performance compared to polymers made using the benchmark monomer, 4,4′-(hexafluoroisopropylidene)diphthalic anhydride. In particular, polymers from TNTDA and 2,6-diaminotriptycene (DAT) exhibited the best performance, with CO2/CH4 and O2/N2 separation metrics approaching or surpassing the 2008 Robeson upper bounds, because of the presence of additional ultramicropores related to the internal free volume of the triptycene moiety.

Renal fibrosis is a non-negligible pathological change in chronic kidney disease (CKD). Increasing evidence indicates that macrophage and gut-kidney axis are correlated with CKD. In this study, we manifest that pharmacological modulating macrophage phenotype via gut-kidney axis is conducive to the alleviation of renal fibrosis. Employing wild-type male mice with unilateral ureteral obstruction (UUO), renal fibrosis was dramatically mitigated in mice treated with antibiotics. And antibiotics application restricted the synthesis of intestinal flora metabolite Trimethylamine N-Oxide (TMAO). However, a 1.3% choline diet enhanced fibrosis. Then we further examined macrophage phenotype through the gut-kidney axis. In in vivo and in vitro culture experiments, the mRNA expression of Nos2, Tnf-α, Il-6, and Il-1β increased under TMAO stimulation. Curbing the NLRP3 inflammasome countered TMAO-induced M1 polarization in bone marrow-derived macrophages. This finding demonstrates that NLRP3 plays a critical part in macrophage polarization. Because of the declining M1 polarization trend in the early stage, M2 macrophages undoubtedly decreased in the tissues. Our results revealed that some metabolites could regulate macrophage phenotype, which matters the severity of renal fibrosis. Thus, pharmacological targeting macrophage phenotype via gut-kidney axis may be a different strategy to treat renal fibrosis.

In order to explore the kinematics and muscle force characteristics of competitive Taijiquan arm manipulation, and solve the problems of arm trajectory and control in the process of manipulation, this study puts forward the sports biomechanical analysis of arm manipulation in competitive Taijiquan. The technical characteristics and muscle force characteristics of 15 athletes from the competitive Taijiquan team of Xi’an Institute of physical education were studied. Use Excel 2007 and SPSS17.0 to statistically analyze and process the original data. According to the actual needs, the data indicators are summarized. The combined movements of competitive Taijiquan arm manipulation are captured through high-speed photography, and the kinematic data are statistically analyzed, mainly from the two aspects of action amplitude change and action braking. The results show the action track length, relative track length, and action track length of each plane of the two combined hands. The order of the two combined action tracks is: combination 1 > combination 2, in which the action track in the sagittal plane is the longest in combination 1, and it can also be considered that the motion amplitude in the sagittal plane is the largest in combination 1. The average acceleration of group A in the first beat is 0.51 m/s2 smaller than that of group B, and the value is 0.22 m/s2 smaller. Therefore, the deceleration of group A is larger than that of group B, and the braking capacity of group A is slightly stronger than that of group B. In the second beat, the average acceleration of group B is 1.5722 m/s2 larger than that of group A, and the value is 0.210 m/s2 larger. The average acceleration of group A in the third, fourth, fifth, and sixth beats is 0.9, 3.728, 0.57, and 0.837 m/s2 smaller than that of group B, and the values are 0.466, 0.174, 0.250, and 0.003 m/s2 smaller, indicating that the braking capacity of group A in the third, fourth, fifth, sixth, and eighth beats is slightly stronger than that of group B. In the braking of each beat in combination 1 and combination 2 of group AB, the braking ability of arm manipulation of group A is stronger than that of group B. In competitive Taijiquan, the movement techniques of manipulation include: bouncing technology, braking technology, and control technology. For arm manipulation, athletes should have the ability of “braking” technology. In the correlation analysis of movement track length, RMS and I EMG, the score of athletes in group A is high, and there is no correlation between movement track length and RMS. There is a significant correlation between RMS and movement track length in group B, and the correlation degree is moderate. This shows that when the movement of group B athletes is completed, the muscles are in a state of tension, the movement skills are not mastered well, and the energy saving is not achieved. During training, we should pay more attention to the proprioception of muscles and form a correct way of muscle exertion.

Summary Engineers commonly expect symmetric fracture wings in multiple-transverse-fracture horizontal wells. Microseismic surveys have shown that asymmetric hydraulic fractures grow away from the recent fractured wells and grow toward previously produced wells. This might be caused by the elevated stress around the recently fractured well and the reduced stress near the depleted wells. This paper presents the asymmetric fracture growth observed by the microseismic events, develops a simple model to simulate the fracture propagation, and discusses its effect on the well productivity. Motivated by the microseismic observations, we developed a simple 2D fracture model to simulate asymmetric fracture wings that can capture the behavior of fracture hits between two adjacent horizontal fractured wells. Fluid leakoff during fracture propagation is considered in the model. The effect of asymmetric fractures on production is evaluated with numerical simulations. The newly developed fracture model shows that the fracture can grow asymmetrically if the horizontal well is near where the stress field is different between its two sides. Numerical simulation is used to quantify the productivity reduction caused by asymmetric hydraulic fractures. Our results provide a reason for why asymmetric fractures occur and demonstrate that they do penalize well performance. Our model suggests the importance of fracturing under a balanced-stress distribution that benefits long-term production. Use of this model also suggested that an optimized hydraulic-fracturing-treatment design will improve the overall performance of multiple parallel wells, which minimizes or avoids asymmetric fracture wings. The fracture-propagation model and productivity model provide simple but profound guidelines for well-pad management, including well spacing, stage planning and spacing, and completion and production order.

The first observation of the Ω b - → Ξ c + K - π - decay is reported using p p collision data at center of mass energies of 7, 8, and 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb - 1 . Four excited Ω c 0 baryons are observed in the Ξ c + K - mass projection of the Ω b - → Ξ c + K - π - decays with the significance of each exceeding five standard deviations. They coincide with the states previously observed in prompt p p and e + e - production. Relative production rates, masses, and natural widths of the states are measured, and a test of spin hypotheses is performed. Moreover, the branching ratio of Ω b - → Ξ c + K - π - is measured relative to the Ω b - → Ω c 0 π - decay mode and a precise measurement of the Ω b - mass of 6044.3 ± 1.2 ± 1. 1 - 0.22 + 0.19 MeV is obtained.

Vogt, Bruno/0000-0002-1548-6387; Dufek, Stephanie/0000-0002-6323-6673; Liu, Lili/0000-0002-2622-9669; Paczek, Leszek/0000-0003-0160-3009; Cui, Zhao/0000-0002-5837-1926; amoroso, antonio/0000-0002-9437-9407; Rosen, Raphael/0000-0003-1025-1965; Loos, Ruth/0000-0002-8532-5087; coenen, marieke/0000-0001-8796-2031; zanoni, francesca/0000-0001-9567-6713; CUCCA, Francesco/0000-0002-7414-1995; Ars, Elisabet/0000-0002-4118-4358; Hamilton, Patrick/0000-0001-6703-3745 WOS:000563559600001 PubMed ID: 32231244 Membranous Nephropathy (MN) is a rare autoimmune cause of kidney failure. Here we report a genome-wide association study (GWAS) for primary MN in 3,782 cases and 9,038 controls of East Asian and European ancestries. We discover two previously unreported loci, NFKB1 (rs230540, OR = 1.25, P = 3.4 x 10(-12)) and IRF4 (rs9405192, OR = 1.29, P = 1.4 x 10(-14)), fine-map the PLA2R1 locus (rs17831251, OR = 2.25, P = 4.7 x 10(-103)) and report ancestry-specific effects of three classical HLA alleles: DRB1*1501 in East Asians (OR = 3.81, P = 2.0 x 10(-49)), DQA1*0501 in Europeans (OR = 2.88, P = 5.7 x 10(-93)), and DRB1*0301 in both ethnicities (OR = 3.50, P = 9.2 x 10(-23) and OR = 3.39, P = 5.2 x 10(-82), respectively). GWAS loci explain 32% of disease risk in East Asians and 25% in Europeans, and correctly re-classify 20-37% of the cases in validation cohorts that are antibody-negative by the serum anti-PLA2R ELISA diagnostic test. Our findings highlight an unusual genetic architecture of MN, with four loci and their interactions accounting for nearly one-third of the disease risk. National Institute for Diabetes and Digestive Kidney Diseases (NIDDK) [RC2-DK116690, R01-DK105124, R01-DK097053, R01-DK108805]; National Institute on Minority Health and Health Disparities (NIMHD)United States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute on Minority Health & Health Disparities (NIMHD) [R01-MD009223]; Charles Woodson Clinical Research Fund; Nephrotic Syndrome Study Network Consortium (NEPTUNE) [U54-DK-083912]; Columbia University, Columbia Glomerular Center; Office of Rare Diseases Research, National Center for Advancing Translational Sciences (NCATS); National Institute of Diabetes, Digestive, and Kidney Diseases (NIDDK)United States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Institute of Diabetes & Digestive & Kidney Diseases (NIDDK); University of MichiganUniversity of Michigan System; NephCure Kidney International; Halpin Foundation; National Key Research and Development Program of China [2016YFC0904100]; Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [81621092]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [81870460, 81570598]; Science and Technology Innovation Action Plan of Shanghai Science and Technology Committee [17441902200]; Shanghai Municipal Education Commission, Gaofeng, Clinical Medicine Grant [20152207]; Shanghai Jiao Tong University School of Medicine, Multi-Center Clinical Research Project [DLY201510]; International Cooperation and Exchange Projects of Shanghai Science and Technology Committee [14430721000]; Outstanding Young Scholar Award [81622009]; Shanghai Health and Family Planning Committee Hundred Talents Program [2018BR37]; Seoul National University Hospital Human Biobank, a member of the National Biobank of Korea - Ministry of Health and Welfare, Republic of Korea; MRCMedical Research Council UK (MRC) [MR/J010847/1]; Manchester Academic Health Science Centre [MAHSC 186/200]; Greater Manchester Local Clinical Research Network; Kidneys for Life Charity; David and Elaine Potter Charitable Foundation; St Peter's Trust for Kidney, Bladder and Prostate Research; Kids Kidney Research UKKidney Research UK (KRUK); Kidney Research UKKidney Research UK (KRUK); Italian Ministry of Health grantMinistry of Health, Italy [GR-2011-02350438]; Department of Excellence Grant 2018-2022 - Italian Ministry of Education for the Department of Medical Sciences of the University of Turin; Columbia University; Poznan University of Medical Sciences, Poland; German Ministry of Education and Research (BMBF)Federal Ministry of Education & Research (BMBF) [01ER0804]; KfH Foundation for Preventive Medicine; Bayer Pharma AG; German Research FoundationGerman Research Foundation (DFG) [CRC 1140, KO 3598/3-1, CRC 992]; European Research CouncilEuropean Research Council (ERC) [ERC-2012ADG_2012-0314, 322947]; 7th Framework Programme of the European Community contract [2012-305608]; National Research Agency grant MNaims [ANR-17-CE17-0012-01]; Dutch Kidney Foundation [OW08, KJPB11.021]; National Human Genome Research Institute (NHGRI)United States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANIH National Human Genome Research Institute (NHGRI); NIMHD We are grateful to all study participants across multiple nephrology centres worldwide for their contributions to this work. This work was supported by the following institutions, grants and funding agencies in the US: Columbia University, Columbia Glomerular Center, National Institute for Diabetes and Digestive Kidney Diseases (NIDDK) grants RC2-DK116690 (K.K., M.K.), R01-DK105124 (K.K.), R01-DK097053 (L.H.B., M.K.), R01-DK108805 (M.G.S.), and National Institute on Minority Health and Health Disparities (NIMHD) grant R01-MD009223 (K.K., A.G.G., A.B.). M.G.S. is additionally supported by the Charles Woodson Clinical Research Fund. The Nephrotic Syndrome Study Network Consortium (NEPTUNE), U54-DK-083912, is a part of the National Institutes of Health (NIH) Rare Disease Clinical Research Network (RDCRN), supported through a collaboration between the Office of Rare Diseases Research, National Center for Advancing Translational Sciences (NCATS) and the National Institute of Diabetes, Digestive, and Kidney Diseases (NIDDK). Additional funding and/or programmatic support for this project has also been provided by the University of Michigan, the NephCure Kidney International and the Halpin Foundation. The recruitment and analysis of the Chinese cohorts were supported by the National Key Research and Development Program of China (2016YFC0904100), Natural Science Foundation of China to the Innovation Research Group (81621092), National Natural Science Foundation of China (No. 81870460, 81570598), Science and Technology Innovation Action Plan of Shanghai Science and Technology Committee (No.17441902200), Shanghai Municipal Education Commission, Gaofeng, Clinical Medicine Grant (No.20152207), Shanghai Jiao Tong University School of Medicine, Multi-Center Clinical Research Project (No.DLY201510), International Cooperation and Exchange Projects of Shanghai Science and Technology Committee (No.14430721000), the Outstanding Young Scholar Award for Zhao Cui (No.81622009), and Shanghai Health and Family Planning Committee Hundred Talents Program for Jingyuan Xie (No.2018BR37). The recruitment of the Korean cohort was supported by the Seoul National University Hospital Human Biobank, a member of the National Biobank of Korea, financed by the Ministry of Health and Welfare, Republic of Korea. P.B. and P.H. acknowledge financial support from MRC project "Autoimmunity in Membranous Nephropathy", grant MR/J010847/1 which funded the sample collection from MN patients across the UK. P.B., P.H. and S.H. acknowledge support from Manchester Academic Health Science Centre (MAHSC 186/200), the Greater Manchester Local Clinical Research Network and Kidneys for Life Charity for supporting research in MN in Manchester. We are grateful to the MENTOR study (clinical trials no. NCT01180036), for contributing blood samples of trial participants. The UK cohort was supported in part by grants from the David and Elaine Potter Charitable Foundation (to S.H.P. and R.K.), St Peter's Trust for Kidney, Bladder and Prostate Research (to D.B., H.C.S., S.H.P. and R.K.), Kids Kidney Research UK and Kidney Research UK (to D.B. and R.K.). The Italian cohorts were supported by the Italian Ministry of Health grant GR-2011-02350438 (G.Z., S.G.) and the Department of Excellence Grant 2018-2022 funded by the Italian Ministry of Education for the Department of Medical Sciences of the University of Turin (A.A.).; The recruitment of Polish cases was sponsored by the Polish Kidney Genetics Network (POLYGENES), a collaborative effort between Columbia University and Poznan University of Medical Sciences, Poland. The full list of POLYGENES collaborators can be found in the Supplementary Materials. The GCKD (German Chronic Kidney Disease) study was funded by grants from the German Ministry of Education and Research (BMBF, No. 01ER0804) and the KfH Foundation for Preventive Medicine, with genotyping supported by Bayer Pharma AG. The list of GCKD investigators can be found in the Supplementary Materials. The work of M.W. and A.K. was funded by the CRC 1140 Initiative and by KO 3598/3-1 and CRC 992 (A.K.) of the German Research Foundation. The work of E.H. and R.A.K.S. was funded by the CRC 1192 from the German Research Foundation (Projects B1 and C1). P.R. is a recipient of European Research Council ERC-2012ADG_2012-0314 grant 322947, 7th Framework Programme of the European Community contract 2012-305608 (European Consortium for High-Throughput Research in Rare Kidney Diseases), and the National Research Agency grant MNaims (ANR-17-CE17-0012-01). The Dutch studies were supported by grants from the Dutch Kidney Foundation to JMH and JFW (Nierstichting Nederland grant OW08 and grant KJPB11.021). We would like to thank the Population Architecture Using Genomics and Epidemiology (PAGE) consortium, funded by the National Human Genome Research Institute (NHGRI) with co-funding from the NIMHD, for providing population controls for this study. For full acknowledgment of the PAGE consortium, please see Supplementary Materials. The funding sources were not involved in the study design, collection, analysis, and interpretation of data, writing of the report, or in the decision to submit the paper for publication.

A novel ortho-substituted Troger's Base (TB) diamine with a pendant tert-butyl-phenyl group, i.e., 2,8-bis(4-(tert-butyl)phenyl)-4,10-diamino-6,12-dihydro-5,11-methanodibenzo[b,f][1,5]diazocine (TTBDA), was synthesized in four steps comprising TB formation, nitration, Suzuki-coupling, and reduction, respectively. The one-step polymerization of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), TTBDA, and 3,9-diamino-4,10-dimethyl-6,12-dihydro-5,11-methanodibenzo[b,f][1,5]diazocine (TBDA2) afforded TB-containing intrinsically microporous co-polyimides (TB-PIMPIs). Molecular modeling results revealed that compared with 6FDA/TBDA2, 6FDA/TTBDA exhibited a more contorted chain conformation and higher chain stiffness. As a result, with a TTBDA percentage of >50%, the copolymers exhibited a higher Brunauer-Emmet-Teller surface area, fractional free volume, total pore volume, and interchain distance compared with 6FDA/TBDA2. On the other hand, the ultra-micropores width (0.8–0.9 nm) of the copolyimides was less than that of 6FDA/TBDA2 because of the space-filling and pore-partitioning effects of the tert-butyl-phenyl groups. The combination of higher pore volumes and smaller ultra-micropores in the copolymers induced a more efficient molecular gas-sieving effect and thus higher diffusion selectivity. All copolyimides showed better gas separation performance in terms of the permeability/selectivity trade-off of O2/N2, CO2/CH4, and CO2/N2 compared with of 6FDA/TBDA2. Such enhanced gas separation performance of TTBDA-derived copolyimides made them promising candidate materials for gas separations, especially O2/N2.

Two isomers of conventional cis-dicyclohexyl-3,3′,4,4′-tetracarboxylic dianhydride (4,4′-HBPDA), i.e. dicyclohexyl-2,3′,3,4′-tetracarboxylic dianhydride (3,4′-HBPDA) and dicyclohexyl-2,2′,3,3′-tetracarboxylic dianhydride (3,3′-HBPDA), were prepared through a four-step procedure. The data from single crystal X-ray diffraction revealed that 3,3′-HBPDA possessed higher structural rigidity/linearity than 4,4′-HBPDA. The one-step polycondensation of isomeric HBPDAs with commercial diamines enabled the synthesis of alicyclic polyimides. The isomer effects of the dianhydrides on the properties of resulting polyimides were studied in detail. For certain diamines, 3,3′-HBPDA-derived polyimides possessed higher glass transition temperatures (Tg) and better dimensional stability compared with those from 4,4′-HBPDA and 3,4′-HBPDA. These phenomena could be attributed to the higher structural rigidity/linearity of 3,3′-dicyclohexyl-tetracarboxydiimide, and restricted rotation of 3-substituted cyclohexylimide. Owing to the asymmetric structures and suppressed rotation of 3-substituted cyclohexylimides, 3,4′-HBPDA-based polymers exhibited higher Tg, improved dimensional stability, and enhanced solubility compared with 4,4′-HBPDA-based ones. Furthermore, all the isomeric HBPDA-derived polyimides were essentially colorless with excellent optical transparency in the UV–Visible region. The excellent overall properties of polyimides from 3,3′-HBPDA and 3,4′-HBPDA made them promising candidate materials for optoelectronic applications.

The chain interactions of hydroxyl polyimide (HPI) precursors, such as chain packing and π-π stacking interactions, significantly affect the microstructures and gas separation performance of the resulting thermally rearranged polybenzoxazoles (TR-PBOs). In this study, HPIs with various 2,2′-substituents in their anhydrides (BPDA-AP, PBPDA-AP, and 12FPBPDA-AP) were prepared through polycondensation of three dianhydrides (4,4′-biphenyltetracarboxylic dianhydride (BPDA), 2,2′-diphenyl-4,4′,5,5′-biphenyltetracarboxylic dianhydride (PBPDA), and 2,2′-bis(3″,5″-ditrifluoromethylphenyl)-4,4′,5,5′-biphenyltetracarboxylic dianhydride (12FPBPDA)) with 2,2′-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (AP). The dihedral angles and rotational barriers for PBPDA and 12FPBPDA were considerably larger than those for BPDA. Thus, the inter- and intra-molecular chain interactions were more pronounced for BPDA-AP than for PBPDA-AP and 12FPBPDA-AP. Consequently, the glass transition and TR temperatures of the HPIs were in the order of BPDA-AP > PBPDA-AP > 12FPBPDA-AP, whereas fractional free volume (FFV) and interchain distances followed the opposite trend. After TR, the FFV and interchain distances of the TR-PBO from BPDA-AP increased more than those from PBPDA-AP and 12FPBPDA-AP, whereas the π-π stacking interactions in BPDA-AP were well maintained. Consequently, BPDA-AP-450 exhibited the highest increase in gas permeability relative to its HPI precursor but the poorest plasticization resistance among fully converted TR-PBOs. This work demonstrated that chain packing played a crucial role in the TR behavior, microstructures, and gas transport properties of TR-PBOs.

Here, a series of intrinsically microporous polyimides (PIM-PIs) were prepared from norbornane-2-spiro-α-cyclopentanone-α′-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride (CpODA) and archetypal contorted diamines, and their microstructures and gas transport properties were systematically investigated and compared with those of the counterparts derived from 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA). For certain diamines, the surface areas, interchain distances, and fractional free volumes (FFV) of the CpODA-derived PIM-PIs were considerably greater than those of the 6FDA-derived ones, and were in the range of 92–567 m2 g−1, 0.575–0.607 nm, and 0.194–0.246, respectively. Consequently, the CpODA-derived PIM-PIs overall displayed higher gas permeabilities and better gas separation performances compared to the 6FDA-derived ones. In particular, CpODA-TBDA2 and CpODA-DAT showed high H2 permeabilities (>600 Barrer) and moderate H2/N2 and H2/CH4 selectivities which approached or even surpassed the corresponding 2008 Robeson upper bounds. The excellent gas separation performance of these CpODA-derived PIM-PIs may be attributed to the contorted and bulky architecture of the CpODA residue, which led to reduced inter- and intra-molecular interactions and the formation of ultramicropores of

A novel alicyclic dianhydride, 2R,5R,7S,10S-naphthanetetracarboxylic dianhydride (HNTDA), was prepared through the hydrogenation of tetramethyl 1,4,5,8-naphthalenetetracarboxylate, followed by deprotection and dehydration reactions. Single crystal X-ray diffraction results revealed that HNTDA possesses an irregular L-shaped architecture with one anhydride ring equatorial, and the other axial on the naphthane ring. Conventional one-step solution polycondensation of HNTDA with commercial diamines enabled the preparation of fully or semi-alicyclic polyimides with sufficient molecular weights. The properties of HNTDA-based polyimides were systematically characterized and compared with their counterparts based on 1S,2R,4S,5R-cyclohexanetetracarboxylic dianhydride (HPMDA). Dynamic mechanical thermal analysis, thermogravimetric analysis, thermal mechanical analysis, and tensile testing indicated that HNTDA-based polymers exhibit markedly higher thermal and mechanical properties compared with HPMDA-based ones. These improvements can be rationalized according to the rigid, bulky, fused naphthanetetracarboxydiimide moiety, and the pronounced inter- and intra-molecular interactions. Furthermore, HNTDA-based polyimides were colorless or pale-yellow, and displayed good optical transparency, although their cutoff wavelength values were higher than those of HPMDA-based ones.

Engineers commonly expect symmetric fracture wings in multiple transverse fracture horizontal wells (MTFHWs). Microseismic surveys have shown asymmetric hydraulic fracture grow away from the recent fractured wells and grow towards previous produced wells. It might be caused by the elevated stress around the recently fractured well and the reduced stress near the depleted wells. This paper presents the asymmetric fracture growth observed by the microseismic events and develops a simple model to simulate the fracture propagation and its impact on the well productivity. Motivated by the microseismic observations, we developed a simple fracture model to simulate asymmetric fracture wings that can capture the behavior of fracture hits between two adjacent horizontal fractured wells. Also, we developed a model to estimate the productivity of a well with asymmetric fractures. The newly developed fracture model shows that the fracture can grow asymmetrically if the horizontal well is located where stress field is different between its two sides. The productivity model for asymmetric hydraulic fractures quantifies the penalty to the well performance. Results provide a reason why asymmetric fractures happen and that they do penalize well performance. Our models suggest the importance of fracturing under balanced stress distribution which benefits the long-term production. Use of the model suggested an optimized hydraulic fracturing treatment design will improve the overall performance of multiple parallel wells that minimizes or avoids asymmetric fracture wings. The fracture propagation model and productivity model provide simple, but profound, guidelines for the well pad management, including well spacing, stage planning and spacing, completion and production order.

Additional file 1: Table S1. Baseline characteristics of different grades of IMN patients. Table S2. Hazards proportional assumption test by COX time-dependant covariates.

Novel dibenzodioxane-containing dianhydride (MMBMDA) and diamine (FDBDA and MMBDA) monomers with sterically hindered contortion sites and pendent fluorene or trimethylbenzene moieties were prepared using 4-methylcatechol as a major reactant. High temperature polycondensation of these monomers and 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) enabled the synthesis of intrinsically microporous polyimides (PIM-PI) with adequately high molecular weights. The surface area, fractional free volume, and d-spacing of these PIM-PIs were 385–543 m2 g-1, 0.179-0.212, and 0.672-0.683 nm, respectively, following the order of MMBMDA-FDBDA > MMBMDA-MMBDA > 6FDA-FDBDA > 6FDA-MMBDA. Moreover, the high rigidity of MMBMDA-based PIM-PIs induced the formation of ultramicropores (

Two novel polyimides incorporating Troger's Base (TB) units, Bio-PITB-1 and Bio-PITB-2, were facilely synthesized from lignin-based imide-containing diamines via TB polymerization. The polymers exhibited excellent thermal stability, finely tuned microporous structures with high BET surface areas (~569 m2 g−1), high fractional free volumes (~0.224), and appropriate inter-chain distances (~0.68 and ~0.38 nm). Mechanically tough Bio-PITB membranes were successfully achieved due to their high molecular weights (~1.24 × 105 g mol−1) and good solubility in organic solvents. Bio-PITBs presented superior gas transport properties with improved gas permeability compared to the previously reported PI-TBs as well as Bio-TBPIs prepared from the same lignin-based dianhydrides but different synthetic routes. As a result, Bio-PITBs located near the 2008 upper bounds in H2/CH4, H2/N2, and CO2/CH4 gas pairs with H2 and CO2 permeabilities over 1000 Barrer. Furthermore, the effects of membrane drying protocols and physical aging on gas transport behaviors of Bio-PITBs were investigated.

A new class of thermally rearranged (TR) polymers was prepared via copolymerization of TR-able o-hydroxyl polyimide and non-TR-able polyimide incorporating highly rigid Troger's Base (TB) units. The effect of TB content, type of TR-able diamine, and TR protocols on polymer properties and gas transport behaviors were thoroughly studied. TB moieties in the copolymers efficiently enhanced polymer rigidity and induced high Tg and TR temperature as confirmed by thermogravimetric analysis and dynamic mechanical analysis. Additionally, as the TB molar ratio increased, the interchain distances of precursor polyimides increased from 0.545 to 0.585 nm. The most important finding in this work was the synergistic effect between TR conversion and TB segments, which provide the optimum contents of TB in the copolymers. As a result, 6F6FTB-0.3-450 presented a maximum d-spacing value of 0.609 nm and excellent gas separation performance of 1567 Barrer for H2 and 1944 Barrer for CO2 along with a selectivity of 18.6 for H2/CH4 and 23.07 for CO2/CH4, surpassing the corresponding 2008 upper bounds. In addition, 6F6FTB-0.3 exhibited good plasticization resistance under CO2/CH4 mixed gas up to CO2 fugacity of ~15 bar.

Ultramicroporous polyimides obtained from bio-based anhydrides were synthesized for gas separation membranes. Two novel dianhydrides, 5,5'-(mesitylmethylene)bis(4-methylphthalic anhydride) (MMDA) and 5,5'-(9H-fluorene-9,9-diyl)bis(4-methylphthalic anhydride) (FDDA), were successfully synthesized from guaiacol, a lignin-based bio-material. Due to the fixed center of o-methyltriphenylmethane and o-methyldiphenylfluorene units, the bio-based dianhydrides had high energy barriers to rotation, resulting in highly rigid polymer chains. After polymerization with a Troger's Base (TB)-containing diamine using a one-step imidization, two kinds of bio-based polyimides incorporating TB units (Bio-TBPI-1 and Bio-TBPI-2) were prepared with reasonable molecular weights and outstanding thermal properties. Bio-TBPIs demonstrated a microporous structure determined by high BET surface areas of ~500 m3 g−1, high fractional free volumes (FFVs) of ~0.2, and d-spacings of ~0.7 nm. In addition, Bio-TBPIs exhibited narrow cavity size distributions around 0.5 nm, and molecular sieving characteristics due to the ultramicroporosity. Bio-TBPI membranes displayed excellent gas separation performance, which was located near the upper bounds of important gas pairs such as H2/CH4, H2/N2, O2/N2, and CO2/CH4. The gas separation performance of Bio-TBPIs was better than that of corresponding TB-based polyimides containing commercial dianhydrides. The effect of physical aging on gas transport behaviors of Bio-TBPIs was monitored for 200 days, resulting in loss of permeability and enhanced selectivities.

A novel bulky and rigid ortho-hydroxyl diamine, 3,3′-diamino-5,5′,6,6′-tetramethyl-[1,1′-biphenyl]-2,2′-diol (TMBDA), was synthesized for gas separation membranes in this study. The chemical structure of TMBDA with four methyl groups and a fixed twist biphenyl center was rationally designed, and consequently presented a superior energy barrier of rotation, which efficiently suppressed chain motion and enhanced polymer rigidity. Four types of TMBDA-based polyimides (PIs) were prepared with two commercially available dianhydrides, i.e., 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and pyromellitic dianhydride (PMDA), from two different synthetic routes, azeotropic and chemical imidization. Thermally rearranged (TR) polymers were obtained from TMBDA-based PIs by thermal treatment at various temperatures. Thermal properties and physicochemical characteristics of TMBDA-based PIs and TR polymers were investigated. The resulting polymers exhibited high glass transition temperatures (Tg) and contorted backbone structures with three discrete d-spacing values, where the smallest interchain d-spacing was located between the kinetic diameters of H2 and CH4 molecules. Moreover, TMBDA-based TR polymers showed outstanding performances in hydrogen separation with comparable H2 permeability and higher selectivity than reported TRs. For instance, 6F-TM-Ac-425 exhibited a H2 permeability of 325 Barrer with H2/CH4 and H2/N2 selectivities of 50 and 39, respectively, approaching to the 2008 Robeson upper bound.