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Oil‐in‐dispersion (O/D) emulsions are the focus in many fields due to their new microstructures and new functions. Herein, O/D emulsions were successfully prepared using series of cationic gemini surfactants 12‐s‐12 (s = 2, 3, and 6) and alumina nanoparticles. The microstructures and type of emulsions were identified using optical microscopy, zeta potential and contact angle methods. Gemini surfactants with two head groups carry more charges than that of conventional surfactants when adsorbed at the oil–water interface. The O/D emulsions can be stabilized at lower surfactant concentrations compared with the conventional single‐headed surfactants. In the presence of 0.1 wt% alumina nanoparticles, gemini surfactants 12‐s‐12 (s = 2, 3, and 6) can stabilize emulsions at the concentration of 3 × 10−4 mM (1.84 × 10−5 wt%), 6 × 10−4 mM (3.76 × 10−5 wt%) and 1 × 10−3 mM (6.68 × 10−5 wt%), respectively. Addition of excessive organic salts such as sodium salicylate and sodium p‐methylbenzenesulfonate shielded the head group charges of gemini surfactants, leading to gemini surfactants to behave as nonionic surfactants Adsorption of surfactants at the alumina nanoparticles occurred, resulting in the transformation from the O/D emulsions to Pickering emulsions. This work shows the advantages of preparing O/D emulsions using gemini surfactants and also provides a new methods of emulsion type transformations by adding excessive oppositely charged organic salts. [ABSTRACT FROM AUTHOR]

We developed an analytical formula to calculate the influence of optical phonons on the mobility of two-dimensional Dirac materials at arbitrary temperature and arbitrary doping concentration. The method was combined with first-principles calculations to show that the effect of optical phonons on mobility is not negligible for typical Dirac materials such as graphene even though the occupation number of optical phonons is relatively small. Unlike the treatment of electron–acoustic phonon coupling, the energy change of electrons in the scattering process with optical phonons is crucial, which leads to a non-power temperature dependence of mobility under weak doping. The formalism was applied to calculate and analyze the mobility of two well-known Dirac materials, α-graphyne and the VCl3 monolayer, which differs by one to two orders of magnitude. [ABSTRACT FROM AUTHOR]

Background: Alzheimer's disease (AD) is accompanied with impaired neurovascular coupling. However, its early alteration remains elusive along the AD continuum. Objective: This study aimed to investigate the early disruption of neurovascular coupling in cognitively normal (CN) and mild cognitive impairment (MCI) elderly and its association with cognition and AD pathologies. Methods: We included 43 amyloid-β-negative CN participants and 38 amyloid-β-positive individuals (18 CN and 20 MCI) from the Alzheimer's Disease Neuroimaging Initiative dataset. Regional homogeneity (ReHo) map was used to represent neuronal activity and cerebral blood flow (CBF) map was used to represent cerebral blood perfusion. Neurovascular coupling was assessed by CBF/ReHo ratio at the voxel level. Analyses of covariance to detect the between-group differences and to further investigate the relations between CBF/ReHo ratio and AD biomarkers or cognition. In addition, the correlation of cerebral small vessel disease (SVD) burden and neurovascular coupling was assessed as well. Results: Related to amyloid-β-negative CN group, amyloid-β-positive groups showed decreased CBF/ReHo ratio mainly in the left medial and inferior temporal gyrus. Furthermore, lower CBF/ReHo ratio was associated with a lower Mini-Mental State Examination score as well as higher AD pathological burden. No association between CBF/ReHo ratio and SVD burden was observed. Conclusion: AD pathology is a major correlate of the disturbed neurovascular coupling along the AD continuum, independent of SVD pathology. The CBF/ReHo ratio may be an index for detecting neurovascular coupling abnormalities, which could be used for early diagnosis in the future. [ABSTRACT FROM AUTHOR]