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Highlights • The static and dynamic functional connectivity patterns altered in motor execution regions after stroke. • Significant correlation was found between the motor function and altered dynamic functional connectivity in stroke patients. • Dynamic properties of functional connections in neural networks might be a potential tool for evaluating motor function after stroke. Abstract The aims of this study were to examine both static functional connectivity (FC) and dynamic FC alterations in motor execution regions after stroke and to investigate whether the altered static or dynamic FC was associated with the clinical behaviors in stroke patients. Seventy-six stroke patients and 55 healthy controls (HC) were recruited. Static FC and dynamic FC maps were computed based on the seeds of six core regions in motor execution network. Correlation analyses were performed between static or dynamic FC and clinical behavioral scores in stroke patients. Compared with the HC, the stroke patients had significantly higher static FC between the seeds and the precentral or postcentral gyrus, frontal gyrus, inferior parietal lobule, thalamus and insula, and lower static FC between the seeds and the cerebellum and middle temporal gyrus. There were significant differences in dynamic FC between the seeds and precuneus, calcarine gyrus, insula, inferior parietal lobule, precentral gyrus, and middle temporal, frontal or occipital gyrus between the stroke patients and HC. Furthermore, a significant negative correlation was found between the Fugl-Meyer assessment scores and dynamic FC of the ipsilesional primary motor cortex and contralesional precentral gyrus in patients. The current study shows that the patterns of both static FC and dynamic FC changed after stroke, and correlation between motor function and temporal variability in the FC of the precentral gyrus was significant in stroke patients. Our findings indicate that dynamic FC might be a potential indicator for evaluating motor function after stroke. [ABSTRACT FROM AUTHOR]

In an oil exploitation process, hydrogel plugging agents can effectively reduce the water-oil intermixing, decrease water extraction volume, and enhance oil recovery rate. The practical applications of traditional polyacrylamide (PAM) hydrogel plugging agents in oilfield are limited by their non-biodegradability, poor mechanical performance, and inferior temperature-resistance. This work developed a mechanically stable and high-temperature-resistant composite hydrogel (STP) by incorporating biodegradable scleroglucan (Slg) and TEMPO-oxidized cellulose nanofibers (TOCN) in the PAM hydrogel. The addition of Slg conferred heat resistance to the PAM hydrogel, while TOCN reinforced the mechanical strength. Anti-aging analyses revealed that the STP endured for 108 h in a saline environment at 140 °C. In the water flooding characterization, the STP displayed a breakthrough pressure of 42.10 psi/ft. at a flow rate of 0.75 cm3/min. Under these extreme conditions, the plugging pressure reached 14.74 psi/ft., meeting the essential criteria for oilfield water plugging. This research demonstrates the potential of polysaccharides in the preparation of sustainable, tough, and heat-resistant water plugging materials. [ABSTRACT FROM AUTHOR]

Nanomaterial-enhanced hydrogels have attracted considerable attention as temporary plugging agents for lost circulation control due to their improved strength under high temperature and high pressure (HTHP) conditions compared to conventional hydrogels. In this study, a pseudointerpenetrating network nanocomposite hydrogel (PINNG), which was composed of temperature-resistant polyacrylamide (TSPAM), polyethyleneimine (PEI) and cellulose nanofibrils (CNFs), was proposed. CNF with a fibrous structure exhibited a more significant effect on the rheological behavior and mechanical strength of the hydrogel than nanosilica (nano-SiO 2). The reversible CNF network endowed the gelant with increased zero-shear viscosity and significant thixotropy. Furthermore, the presence of CNF noticeably improved the strength of PINNG, and the elastic modulus of PINNG was 1232% greater than that of the blank sample. According to analyses of Fourier transform infrared spectroscopy (FTIR), thermogravimetry-derivative thermogravimetry (TG–DTG) and scanning electron microscopy (SEM), it can be deduced that the strengthening mechanism of CNF was mainly related to physical filling, physical crosslinking, and especially the formation of a pseudointerpenetrating network structure with the crosslinked polymer chains. Due to the strengthening effect of CNF, PINNG exhibited a better pressure-bearing performance than the blank sample and the nano-SiO 2 composite sample under 140 °C for the core with 2 mm of fracture width. Additionally, the favorable degradability of the PINNG system demonstrated that PINNG exhibited great potential in the application of lost circulation control as a temporary plugging agent. [Display omitted] [ABSTRACT FROM AUTHOR]

• Ionic liquid surfactants(ILSs) were synthesized by acid-base reaction. • At low concentration, ILSs can form a stable emulsion. • At higher concentration, ILSs can form the interfacial gel. • The interfacial gel is the layered liquid crystal structure. • Gel's static loading capacity can reach 3.98 × 104 Pa/m2. Oleic acid (OA), behenic acid (BA) and N, N -dimethylcyclohexylamine (DMCHA) are used to synthesize two ionic liquid surfactants (ILSs, D-OA and D-BA) by acid-base reaction. ILSs greatly reduce the surface tension of water, and the critical micelle concentrations (CMC) are 5.86 × 10-4 mol/L and 2.57 × 10-6 mol/L, respectively. Different concentrations of D-OA can form a stable emulsion between water and oil, and the droplet size of emulsion with 3 wt% D-OA is mainly concentrated in 3 ∼ 6 μm, while D-BA is difficult to form a stable emulsion. ILSs with concentration greater than 4 wt% can form interfacial gels at the interface of water and oil, and the interfacial gel is analyzed by Polarizing Microscope (POM), Small Angle X-ray Scattering (SAXS), and Scanning Electron Microscope (SEM), confirming it as a layered liquid crystal, and the interlayer spacing is 120.83 Å, indicating that the interlayer contains a large amount of water and oil. Rheological behavior verifies its layered structure with low stability. The interfacial gel can support water for 2,000 times of ILSs weight for about 20 days, verifying its static loading capacity can reach 3.98 × 104 Pa/m2. The interfacial gel also has a certain temperature response with losing the adhesion and stability at high temperature and recovering the illiquidity at low temperature. Salt makes the interfacial gel compressed and its stability reduced. The ILSs realize the transformation from emulsion to gel by self-assembly behavior, that is, the low-concentration ILSs in water are as a single ion or low-dispersed micelle and oil is dissolved into water to form an emulsion, while the high-concentration ILSs are formed wormlike micelles through self-assembly, with oil and water being dissolved to form an interfacial gel to be used as oil–water partitions or channels. [ABSTRACT FROM AUTHOR]