The Altered Reconfiguration Pattern of Brain Modular Architecture Regulates Cognitive Function in Cerebral Small Vessel Disease

Background: Cerebral small vessel disease (SVD) is a common cause of cognitive dysfunction. However, little is known whether the altered reconfiguration pattern of brain modular architecture regulates cognitive dysfunction in SVD.Methods: We recruited 25 cases of SVD without cognitive impairment (SVD-NCI) and 24 cases of SVD with mild cognitive impairment (SVD-MCI). According to the Framingham Stroke Risk Profile, healthy controls (HC) were divided into 17 subjects (HC-low risk) and 19 subjects (HC-high risk). All individuals underwent resting-state functional magnetic resonance imaging and cognitive assessments. Graph-theoretical analysis was used to explore alterations in the modular organization of functional brain networks. Multiple regression and mediation analyses were performed to investigate the relationship between MRI markers, network metrics and cognitive performance.Results: We identified four modules corresponding to the default mode network (DMN), executive control network (ECN), sensorimotor network and visual network. With increasing vascular risk factors, the inter- and intranetwork compensation of the ECN and a relatively reserved DMN itself were observed in individuals at high risk for SVD. With declining cognitive ability, SVD-MCI showed a disrupted ECN intranetwork and increased DMN connection. Furthermore, the intermodule connectivity of the right inferior frontal gyrus of the ECN mediated the relationship between periventricular white matter hyperintensities and visuospatial processing in SVD-MCI.Conclusions: The reconfiguration pattern of the modular architecture within/between the DMN and ECN advances our understanding of the neural underpinning in response to vascular risk and SVD burden. These observations may provide novel insight into the underlying neural mechanism of SVD-related cognitive impairment and may serve as a potential non-invasive biomarker to predict and monitor disease progression

Evaluation of the Moisture Effect on the Material Interface Using Multiscale Modeling

Abstract Layered material systems are widely seen in various engineering applications such as thin films circuit boards in electronic engineering, lipid bilayer in biological engineering, and adhesive bonding in aerospace and civil engineering applications. However, the durability of the material interface can be seriously affected due to the prolonged exposure to water. Although the experimental studies have shown the reduction in terms of ultimate bond strength and fracture toughness for material interface, the shift in failure mode found in experiment cannot be explained using conventional fracture theory, which is related to the interaction between the water and material interface. To understand the debonding mechanism from a fundamental and comprehensive aspect and bridge knowledge from the atomistic scale to continuum scale, multiscale modeling approach has been proposed to study the debonding behavior of material interface under moisture effect. A number of studies have been conducted using multiscale modeling approach to investigate the debonding of material interface, and it is necessary to summarize these studies to understand the role of water molecules in weakening and diffusing at the material interface using different atomistic models, force fields and upscaling techniques. This paper provides a comprehensive review on the multiscale modeling of interfacial and delamination behavior of layered material system under moisture attack with the focus on the molecular dynamics simulation and finite element modeling. The FRP bonded concrete system is used as a representative to demonstrate the approach of multiscale modeling. The future research direction is recommended, which involves the consideration of roughness of substrate and structural voids at interface for the better understanding of durability issue for interface in layered material system under different environmental conditions

Investigation on interfacial defect criticality of FRP-bonded concrete beams

Bonding fiber reinforced polymer (FRP) has been proven to be an effective and efficient method to strengthen and/or retrofit deficient concrete components and structures. Interfacial defects may easily arise due to improper construction or environmental deterioration during the designed service life and they may cause an unfavorable effect on the local bond behavior and global performance of FRP-bonded concrete systems. However, the information on the interfacial defect effect and the guideline for distinguishing the criticality of interfacial defect is limited, making it difficult to assess the long term integrity. In this study, FRP-bonded concrete beams containing various interfacial defects are under four-point bending test to evaluate the defect effect and determine the interfacial defect criticality from location and size aspects. Meanwhile, finite element models representing different sizes of FRP-bonded concrete beams are built and simulated to study the size effect of beam. Both the experimental observation and numerical results indicate that the deep beam is more sensitive to interfacial defect than normal beam. The threshold for critical interfacial defect varies significantly depending on the beam type and defect location. The small, medium and large categories of interfacial defect can be classified according to the beam type, defect location and defect size sequentially. Different maintenance strategies should be adopted corresponding to small, medium and large interfacial defects. The interfacial defect criticality unveiled from this study can provide guidelines for maintenance when defect is detected during inspection and it can be beneficial to a more precise performance evaluation and service life prediction of FRP-bonded concrete structures

Overcoming chloride ions-induced deterioration in compressive strength of mortar by graphene oxide: Experimental study and molecular dynamics simulation

Using seawater to make concrete structures saves freshwater resources and reduces transport costs in offshore construction. However, the presence of chloride ions in mortar causes the formation of Friedel’s salt, which changes the microstructure of cement hydration products. As a result, the compressive strength of the mortar significantly deteriorates due to excessive chloride ions. Graphene oxide (GO) is used to overcome chloride ions-induced deterioration in the compressive strength of mortar in this study. The compressive strength of mortar mixed with chloride ions is increased from 38±5.2 MPa to 44.5±0.2 MPa with the addition of GO. Scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis show the decrease of porosity in mortar with GO and adsorption of chloride ions on GO. Molecular dynamics simulations show that GO yields constraints on the mobility of chloride ions and the improvement of interfacial strength between calcium silicate hydrates

The joint effect of ammonium and pH on the growth of Chlorella vulgaris and ammonium removal in artificial liquid digestate

Although ammonium containing digestate is an ideal alternative medium for microalgae cultivation, high ammonium or unfavorable pH may inhibit microalgal growth. In this study, the joint effect of ammonium and pH on the growth of C. vulgaris and nutrient removal in artificial digestate was investigated. Our results show that ammonium and pH both affected algal growth, but free ammonia (FA) was the main actual inhibitory factor. Algal specific growth rate presented a negative correlation with FA and their relationship was well fitted by a linear regression model. Microalgal growth was little affected below 36.8 mg L-1 FA, while the obvious inhibition occurred at 184 mg L-1 FA (EC50), indicating a high tolerance to FA. Ammonium removal was well described by a first-order kinetics model. FA stress stimulated the production of extracellular organic matters (EOMs), which was good for micmalgae adaptation but adverse to pollutant removal

Experimental Investigation on Interfacial Defect Criticality of FRP-Confined Concrete Columns

Defects between fiber reinforced polymer (FRP) and repaired concrete components may easily come out due to misoperation during manufacturing, environmental deterioration, or impact from external load during service life. The defects may cause a degraded structure performance and even the unexpected structural failure. Different non-destructive techniques (NDTs) and sensors have been developed to assess the defects in FRP bonded system. The information of linking up the detected defects by NDTs and repair schemes is needed by assessing the criticality of detected defects. In this study, FRP confined concrete columns with interfacial defects were experimentally tested to determine the interfacial defect criticality on structural performance. It is found that interfacial defect can reduce the FRP confinement effectiveness, and ultimate strength and its corresponding strain of column deteriorate significantly if the interfacial defect area is larger than 50% of total confinement area. Meanwhile, proposed analytical model considering the defect ratio is validated for the prediction of stress–strain behavior of FRP confined columns. The evaluation of defect criticality could be made by comparing predicted stress–strain behavior with the original design to determine corresponding maintenance strategies

NIR-Responsive Photocatalytic Activity and Mechanism of NaYF₄:Yb,Tm@TiO₂ Core–Shell Nanoparticles

Core–shell structured nanoparticles for near-infrared (NIR) photocatalysis were synthesized by a two-step wet-chemical route. The core is composed of upconversion luminescence NaYF₄:Yb,Tm prepared by a solvothermal process, and the shell is anatase TiO₂ nanocrystals around NaYF₄ particles formed via a method similar to a Stöber process. Methylene blue compound as a model pollutant was used to investigate the photocatalytic activity of NaYF₄:Yb,Tm@TiO₂ composites under NIR irradiation. To understand the nature of NIR-responsive photocatalysis of NaYF₄:Yb,Tm@TiO₂, we investigated the energy transfer process between NaYF₄:Yb,Tm and TiO₂ and the origin of the degradation of organic pollutants under NIR radiation. Results indicate that the energy transfer route between NaYF₄:Yb,Tm and TiO₂ is an important factor that influences the photocatalytic activity significantly and that the degradation of organic pollutants under NIR irradiation is caused mostly by the oxidation of reactive oxygen species generated in the photocatalytic reaction, rather than by the thermal energy generated by NIR irradiation. The understanding of NIR-responsive photocatalytic mechanism helps to improve the structural design and functionality of this new type of catalytic material