Micro Magnetic Field Produced by Fe3O4 Nanoparticles in Bone Scaffold for Enhancing Cellular Activity

The low cellular activity of poly-l-lactic acid (PLLA) limits its application in bone scaffold, although PLLA has advantages in terms of good biocompatibility and easy processing. In this study, superparamagnetic Fe3O4 nanoparticles were incorporated into the PLLA bone scaffold prepared by selective laser sintering (SLS) for continuously and steadily enhancing cellular activity. In the scaffold, each Fe3O4 nanoparticle was a single magnetic domain without a domain wall, providing a micro-magnetic source to generate a tiny magnetic field, thereby continuously and steadily generating magnetic stimulation to cells. The results showed that the magnetic scaffold exhibited superparamagnetism and its saturation magnetization reached a maximum value of 6.1 emu/g. It promoted the attachment, diffusion, and interaction of MG63 cells, and increased the activity of alkaline phosphatase, thus promoting the cell proliferation and differentiation. Meanwhile, the scaffold with 7% Fe3O4 presented increased compressive strength, modulus, and Vickers hardness by 63.4%, 78.9%, and 19.1% compared with the PLLA scaffold, respectively, due to the addition of Fe3O4 nanoparticles, which act as a nanoscale reinforcement in the polymer matrix. All these positive results suggested that the PLLA/Fe3O4 scaffold with good magnetic properties is of great potential for bone tissue engineering applications

Graphene oxide-driven interfacial coupling in laser 3D printed PEEK/PVA scaffolds for bone regeneration

Blending Polyetheretherketone (PEEK) with Polyvinyl alcohol (PVA) is promising to obtain a composite scaffold combining the excellent biomechanical properties of PEEK and the remarkable degradability of PVA. However, the weak interfacial bonding between nonpolar PEEK and polar PVA would result in poor mechanical properties. In this study, owing to its unique amphiphilic properties, graphene oxide (GO) was employed to enhance the interfacial bonding between PEEK and PVA in PEEK/PVA scaffolds that were fabricated by laser 3D printing. On the one hand, the large π-conjugated structure of GO formed strong π-π interactions with the benzene rings in PEEK. On the other hand, the oxygen-containing groups of GO formed strong hydrogen bonds with the hydroxyl groups of PVA. As a result, the interfacial free energy between PEEK and PVA decreased from 37.4 to 29.6 mJ/m2 according to the harmonic-mean rule, and the PVA phase in PEEK matrix became much fine and uniform, indicating a reinforced interfacial bonding. Correspondingly, the strength and modulus of PEEK/PVA scaffolds increased by 97.16% and 147.06%, respectively, for a GO loading of 1%. Furthermore, the scaffolds exhibited good hydrophilicity and degradability, and promoted cell attachment and proliferation in vitro and osteogenic differentiation and bone regeneration in vivo

The influence of childhood emotional neglect experience on brain dynamic functional connectivity in young adults

ABSTRACTBackground: Childhood emotional neglect (CEN) confers a great risk for developing multiple psychiatric disorders; however, the neural basis for this association remains unknown. Using a dynamic functional connectivity approach, this study aimed to examine the effects of CEN experience on functional brain networks in young adults.Method: In total, 21 healthy young adults with CEN experience and 26 without childhood trauma experience were recruited. The childhood trauma experience was assessed using the childhood trauma questionnaire (CTQ), and eligible participants underwent resting-state functional MRI. Sliding windows and k-means clustering were used to identify temporal features of large-scale functional connectivity states (frequency, mean dwell time, and transition numbers).Result: Dynamic analysis revealed two separate connection states: state 1 was more frequent and characterized by extensive weak connections between the brain regions. State 2 was relatively infrequent and characterized by extensive strong connections between the brain regions. Compared to the control group, the CEN group had a longer mean dwell time in state 1 and significantly decreased transition numbers between states 1 and 2.Conclusion: The CEN experience affects the temporal properties of young adults’ functional brain connectivity. Young adults with CEN experience tend to be stable in state 1 (extensive weak connections between the brain regions), reducing transitions between states, and reflecting impaired metastability or functional network flexibility

Biodegradation mechanisms of selective laser-melted Mg–xAl–Zn alloy: grain size and intermetallic phase

Grain size and intermetallic phase were two key factors affecting the biodegradation behaviour of Mg alloys. In the paper, different grain size and intermetallic phase volume fraction were obtained by introducing Al into Mg–Zn alloy via selective laser melting. Results showed that the grain size refined while the intermetallic phase volume fraction increased with Al increasing. As Al was less than 3 wt.%, the grain refinement was the major factor affecting the degradation behaviour. The finer grain would create many grain boundaries, making the alloy passivate readily and resulted in a reduced degradation rate. However, with Al further increasing, the intermetallic phase became the main factor influencing the degradation behaviour though grain size was further refined. The large intermetallic phase volume fraction caused severe galvanic corrosion, accelerating the degradation. This work may provide guidance for balancing grain size and intermetallic phase on degradation behaviour of Mg alloys

Assessing long-term stability of cadmium and lead in a soil washing residue amended with MgO-based binders using quantitative accelerated ageing

A soil washing residue (SWR) (containing 90% clay, cadmium (Cd2+) of 132 mg/kg, lead (Pb2+) of 3410 mg/kg) was stabilized with MgO (M) and MgO + bioapatite (MB) respectively at a dosage of 5% in w/w. The stability of the metals in original and amended SWRs was assessed after immediate treatment and using a laboratory accelerated ageing method simulating 26, 52, 78 and 104 years in field conditions. The dissolved Cd2+ and Pb2+ from the SWR in Toxicity Characteristic Leaching Procedure (TCLP) leachates significantly reduced (by 96.84–99.06%) by both amendments after immediate treatment. The stabilization remained effective within simulated 26 years as the TCLP leached Cd2+ and Pb2+ kept below regulatory levels. This immobilization was mainly due to the increased non-bioavailable Cd2+ and Pb2+ from sequential extraction tests in SWR by the amendments. At simulated 52 years, the TCLP leached Cd2+ from M and MB exceeded regulatory level by 106% and 1% respectively. Large amounts of Cd2+ and Pb2+ were leached out by 36.74–48.18% regardless of the treatments at simulated 104 years. Although bioapatite can significantly aid the stabilization of metals by MgO, the stabilization effectiveness for both treatments diminished at simulated 52 years and from 52 to 104 years

Factors Influencing the Molecular Compositions and Distributions of Atmospheric Nitrogen-Containing Compounds

Atmospheric nitrogen-containing organic compounds (NOCs) are critical components of global nitrogen deposition and light-absorption species. The sources and compositions of NOCs are complex and remain largely unknown. Here, NOCs in 55 ambient aerosol samples collected in Guangzhou, South China, were analyzed via ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry in negative-ion and positive-ion electrospray ionization (ESI) modes. The molecular compositions of NOCs measured via ESI- and ESI+ exhibited considerable differences. NOCs detected in the negative mode were mainly composed of highly oxygenated organic nitrates (O/N = 6), whereas NOCs detected in the positive mode were mainly composed of reduced nitrogen-containing compounds (e.g., amides and amino acids). CHN compounds potentially corresponding to amines and alkaloids showed low abundance in the detection modes. Non-metric multidimensional scaling and individual compound correlation analyses showed that the molecular compositions of NOCs were mainly affected by anthropogenic activities and meteorological parameters. For example, anthropogenic activities such as biomass burning and secondary nitrogen-chemistry processes led to the accumulation of aromatic and highly oxygenated NOCs during winter. During summer, higher OH radical concentrations and temperatures will result in more prevalent or persistent reduced aliphatic NOCs, particularly lipid-like amines. Some variables (e.g., relative humidity) have distinct effects on the variation of different types of NOCs. More research is needed to reveal the influencing mechanisms. This study clarifies the molecular compositions of NOCs and the mechanisms by which various factors influence the molecular variations. The findings can guide the assessment of NOCs evolution and deposition

Research on Thermal-Mechanical Properties of GaN Power Module Based on QFN Package by Using Nano Copper/Silver Sinter Paste

The wide-bandgap semiconductors represented by GaN have a broad application prospect because of their high service temperature and high switch frequency. Quad-Flat-No-Lead (QFN) Package is currently one of the mainstream packaging methods due to its low cost and high efficiency. However, the low reliability of QFN used in GaN devices is still a crucial problem caused by elevated temperatures and the thermal stress induced by the mismatch of coefficient of thermal expansion (CTE). Therefore, it is necessary to control the temperature inner the package and increase the mechanical property of the bonding layer. In this paper, the finite element method (FEM) with thermal-mechanical coupling is performed to optimize the reliability of the bonding layer by adopting sinter nano Cu and silver. Based on the conventional QFN package module, we tried to add different metallization on the bonding surface to decrease the influence of CTE mismatch. We should note that the Anand viscoplastic model was used in the materials of Sintered Ag and lead-free solder paste presented by SAC305, which were the most commonly used in die-attachment. The results showed that the utilization of nano copper/silver paste could hardly facilitate thermal performance although sintered Ag had excellent thermal conductivity. Since the Anand modules of Ag and SAC305 were different, there were some impacts on the stress distribution and deformation. During the bonding process, a large thermal stress generated between die-attachment layer and Package or the PCB. The die-attachment layer formed by nano Ag paste suffered the smaller thermal stress because its CTE is comparable to that of thermal pad. In terms of sintered Ag, the bonding layer generated more elastic strain. As the deformation recovered to initial stage, the stress decreased because of the elastic strain. And we also found that the Ag metallization could decreased the maximum stress of model at heating stage. But Ag metallization suffered larger thermal stress as the temperature decreased. The selection of connection materials and metallization are a crucial part of design the structure of electronic package. And this paper could provide a reference for optimize the package structure to further improve their reliability in future works.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Components, Technology and MaterialsBio-Electronic

Microstructure Evolution and Biodegradation Behavior of Laser Rapid Solidified Mg–Al–Zn Alloy

The too fast degradation of magnesium (Mg) alloys is a major impediment hindering their orthopedic application, despite their superior mechanical properties and favorable biocompatibility. In this study, the degradation resistance of AZ61 (Al 6 wt. %, Zn 1 wt. %, remaining Mg) was enhanced by rapid solidification via selective laser melting (SLM). The results indicated that an increase of the laser power was beneficial for enhancing degradation resistance and microhardness due to the increase of relative density and formation of uniformed equiaxed grains. However, too high a laser power led to the increase of mass loss and decrease of microhardness due to coarsened equiaxed grains and a reduced solid solution of Al in the Mg matrix. In addition, immersion tests showed that the apatite increased with the increase of immersion time, which indicated that SLMed AZ61 possessed good bioactivity