Thermothickening polymers are a novel type of material developed for enhanced oil recovery applications in high-temperature and high-salinity oil reservoirs. However, the existing synthesis process of thermoviscosifying polymers is complex and of high cost, both of which limit the wide application of thermoviscosifying polymers. In this study, a thermothickening water-soluble polymer (PHAD) with a low concentration was synthesized by a "graft from" method, with acrylamide and diacetone acrylamide as grafted monomers and hydroxypropyl methyl cellulose as the backbone chain. The basic parameters for PHAD copolymers were systematically studied in comparison with their homopolyacrylamide counterpart. The results show that the PHAD copolymers exhibited excellent thermothickening ability even when the polymer concentration was 0.2 wt % (total salinity is 9350.08 mg·L–1) upon increasing the temperature from 25 to 90 °C, where the apparent viscosity enhancement changes from 4.0 to 13.3 times with increasing the diacetone acrylamide content in PHAD copolymers. The PHAD copolymers also showed good salt tolerance, thermal stability, and viscoelastic properties under harsh reservoir conditions, which are attributed to the synergistic effect of the rigid heterocyclic ring structure and hydrophobic intermolecular association of thermoresponsive monomers within polymer chains. Moreover, the core displacement experiment and etched glass microscopic model show that the PHAD copolymers have good migration in porous media. Due to its high sweep efficiency, the PHAD copolymer has a higher recovery factor (14.0%) than polyacrylamide (4.3%), which makes it more suitable for salt-tolerant and temperature-tolerant tertiary oil recovery chemicals.
Abstract Previous studies have suggested that the morphology and function of the thalamus and cortex are abnormal in patients with knee osteoarthritis (KOA). However, whether the thalamocortical network is differentially affected in this disorder is unknown. In this study, we examined functional and effective connectivity between the thalamus and major divisions of the cortex in 27 healthy controls and 27 KOA patients using functional magnetic resonance imaging. We also explored the topological features of the brain via graph theory analysis. The results suggested that patients with KOA had significantly reduced resting‐state functional connectivity (rsFC) of the thalamo–sensorimotor pathway; enhanced rsFC of the thalamo–medial/lateral frontal cortex (mFC/LFC), parietal, temporal and occipital pathways; reduced effective connectivity of the left sensorimotor‐to‐thalamus pathway; and enhanced effective connectivity of the right thalamus‐to‐sensorimotor pathway compared with healthy controls. The functional connectivity of the thalamo–sensorimotor and thalamo–mFC pathways was enhanced when patients performed the multisource interference task. Moreover, patients with KOA presented altered nodal properties associated with thalamocortical circuits, including the thalamus, amygdala, and regions in default mode networks, compared with healthy controls. The correlation analysis suggested a significant negative correlation between thalamo–mFC rsFC and pain intensity, between thalamo–sensorimotor task‐related connectivity and disease duration/depression scores, and a positive correlation between right frontal nodal properties and pain intensity in KOA patients. Taken together, these findings establish abnormal and differential alterations in the thalamocortical network associated with pain characteristics in KOA patients, which extends our understanding of their role in the pathophysiology of KOA.
Abstract The development of low‐temperature lithium–sulfur batteries (LSB) has been suppressed by rather poor sulfur utilization and cycle performance, caused by planar Li 2 S growth, hindered lithium polysulfides (LiPSs) transformation, and poor stability of the anode. Recently, low‐concentration electrolytes (LCE) have been employed as promising solutions to solve the above issues. However, aggregation and deposition behavior of polysulfides have been rarely studied. In this work, by comparing the performance of 0.1 and 1 m LiFSI electrolytes, LCEs are proven beneficial for low‐temperature LSBs via new fundamental insights. According to growth pattern analyses by both morphology observation and theoretical models, Li 2 S nucleation in LCEs switch into progressive mode with less initial nuclei, which favors the vertical growth of Li 2 S, resulting in a more complete lithium–sulfur conversion reaction under cold conditions. Through visual experiments, computational simulation, and progressive electrochemical impedance spectroscopy, the ability of LCEs to suppress LiPSs clustering is supported and this anti‐clustering ability effectively enhances the Li–S conversion reaction kinetics. Moreover, in LCEs a protective SEI with LiF and Li 2 S/Li 2 S 2 is likely to form on and stabilize the anode. As a whole, the boosting effect and the mechanism of LCEs enlighten future designs on low‐temperature electrolytes for high‐performance cryogenic LSBs.
The successful growth of colloidal lead halide perovskite quantum dots (PQDs) has generated tremendous interest in the community, due to the unique properties and the promise PQDs offer for use in applications involving light-emitting devices and solar cell technology. However, tangible progress in probing their fundamental properties and/or their integration into optoelectronic devices has been hampered by issues of colloidal and photophysical instability. Here, we introduce a promising surface coating strategy relying on a polyzwitterion polymer, where high-affinity binding onto the QDs is driven by multicoordinating electrostatic interactions with the ion-rich surfaces of CsPbBr3 PQDs. The polymer ligands were synthesized by installing a stoichiometric mixture of amine-modified sulfobetaine anchors and solubilizing motifs on poly(isobutylene-alt-maleic anhydride), PIMA, via nucleophilic addition reaction. We find that this coating approach imparts enhanced colloidal and photophysical stability to the nanocrystals over a broad range of solvent conditions and in powder form. This approach also allows easy phase transfer of the PQDs from nonpolar media to an array of solutions with varying polarities and properties. Additionally, the stabilization strategy preserves the photophysical and structural characteristics of the nanocrystals over a period extending to 1.5 years under certain conditions.
Abstract Formamidinium (CH(NH 2 ) 2 , FA) lead halide perovskites exhibit excellent optoelectronic properties for the applications of light‐emitting diodes and lasers. However, the reported formamidinium lead bromide (FAPbBr 3 ) perovskite‐based lasers mainly depend on the external feedback or Fabry–Pérot mode cavities and suffer from moderate quality ( Q ) factors. Herein, solution‐processed square and quasi‐circular FAPbBr 3 microdisks are developed to achieve room‐temperature naturally facet‐formed whispering gallery mode (WGM) lasers. These microdisks exhibit relatively high Q factor and tunable laser modes with threshold of 10–70 µJ cm −2 under 400 nm excitation. Although the synthesized circular microdisk is not regular enough, it still shows higher Q factor of 3455 than that of square microdisk due to the less boundary wave and pesudointegrable leakage. This simple and low‐cost solution processed method can tackle the complicated and expensive conventional preparation techniques of circular microdisks. Power dependent photoluminescence decay transients indicate that the band edge emission of the FAPbBr 3 microdisks originates from free carrier recombination. In addition, these microdisks show high photostability and that room temperature lasing can sustain over 50 min. These results suggest that FAPbBr 3 microdisks can serve as promising WGM lasers with excellent light emission capability and stability toward practical optoelectronic applications.
Abstract Previous studies have suggested abnormal morphology and function of the thalamus and cortex in KOA. However, it is not known whether the thalamocortical network is differentially affected in this disorder. In this study, we examined functional and effective connectivity between thalamus and the major divisions of the cortex in 27 healthy controls and 27 KOA participants using functional magnetic resonance imaging. We also explored the topological features of the whole brain based on graph theory analysis. The results suggested that patients with KOA had significantly reduced resting-state functional connectivity (rsFC) of the thalamo-sensorimotor pathway, enhanced rsFC of the thalamo-medial/lateral frontal cortex (mFC/LFC), parietal, lateral temporal and occipital pathways, decreased effective connectivity of the left sensorimotor-to-thalamus pathway and enhanced effective connectivity of the right thalamus-to-sensorimotor pathway as compared with of healthy controls. The functional connectivity of the thalamo-sensorimotor and thalamo-mFC pathways was enhanced when performing multi-source interference task. Moreover, patients with KOA showed changed nodal properties associated with thalamo-cortical circuits including the medial and dorsal superior/middle frontal gyrus, inferior parietal gyrus, left thalamus, etc. as compared with healthy controls. Correlation analysis suggested significant negative correlation between thalamo-mFC’s rsFC and pain intensity, between thalamo-sensorimotor task-related connectivity and disease duration/depression scores, as well as positive correlation between right frontal nodal properties and pain intensity in KOA. Taken together, these findings establish abnormal and differential alterations of the thalamocortical network associated with pain characteristics in KOA, which extends our understanding of its’ role in the pathophysiology of KOA.
Dopants are utilized to enhance the mobility and optimize energy levels of hole-transporting layers in perovskite solar cells (PSCs), which are crucial to achieving high power conversion efficiencies (PCEs) of normal PSCs. However, the traditional method of doping 2,2′,7,7′-tetrakis(N,N-di(4-methoxyphenyl)amino)-9,9-spirobifluorene (Spiro-OMeTAD) with lithium bis(trifluoromethylsulfonyl)imide (Li-TFSI) can cause inward migration of Li-ions to perovskite, which is one of the main factors affecting the long-term stability of PSCs. In this study, we utilized a multifunctional ion-migration inhibitor at the Spiro-OMeTAD/perovskite interface to control ion migration. As a result, both Spiro-OMeTAD and perovskite were safeguarded and the device's operational stability was enhanced. The optimized devices with 4-methanesulfonyl-benzamidine hydrochloride exhibited an improved PCE of up to 25.3%. Meanwhile, we documented 520-h T90 under continuous 1-sun illumination, 740-h T80 heating at 60 ± 5 °C, and 1000-h T92 at maximum power point tracking at 50 ± 5 °C under continuous 1-sun illumination.
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