The Structural, Electronic, and Optical Properties of Ge/Si Quantum Wells: Lasing at a Wavelength of 1550 nm

The realization of a fully integrated group IV electrically driven laser at room temperature is an essential issue to be solved. We introduced a novel group IV side-emitting laser at a wavelength of 1550 nm based on a 3-layer Ge/Si quantum well (QW). By designing this scheme, we showed that the structural, electronic, and optical properties are excited for lasing at 1550 nm. The preliminary results show that the device can produce a good light spot shape convenient for direct coupling with the waveguide and single-mode light emission. The laser luminous power can reach up to 2.32 mW at a wavelength of 1550 nm with a 300-mA current. Moreover, at room temperature (300 K), the laser can maintain maximum light power and an ideal wavelength (1550 nm). Thus, this study provides a novel approach to reliable, efficient electrically pumped silicon-based lasers

DCX and LIS1 function in radial and lateral neuronal migration in developing cerebral cortex

Neuronal migration is a fundamental process in developing cerebral cortex. During embryonic development, progenitors are located in the neuroepithelium that surrounds the ventricular lumen in the telencephalon. Progenitors divide and give rise to postmitotic daughter neurons. These neurons migrate to form a stereotyped laminar and radial organization in the maturing cerebral cortex. To understand the molecular and cellular mechanism of neuronal migration is a crucial step in not only elucidating the biology of brain development, but also in gaining greater insight into the pathogenesis of human neurological diseases linked to cortical malformation such as mental retardation, epilepsy, dyslexia and schizophrenia. Two innovative studies presented in this thesis further our understanding of the function of Doublecortin (DCX) and Lissencephaly 1 (LIS1) protein molecules in neuronal migration. The first study combines in utero electroporation and RNA interference (RNAi)-medicated acute knockdown of DCX to reveal the definitive function of DCX in radial migration, a major neuronal migration pathway in developing cerebral cortex. Utilizing similar techniques with high degree of spatial control, the second study shows shared, distinct and interdependent roles of DCX and LIS1 in the lateral cortical stream (LCS), a migration route for cells that populate ventral telencephalon including the piriform cortex and amygdala.

Microstructure and bond strength of niobium carbide coating on GCr15 prepared by in-situ hot press sintering

The hardness and adhesion of protective hard coatings to the substrate are the most important parameters that influence the performance of the tool. Herein, we propose an effective strategy, by in-situ hot press sintering, to fabricate a novel niobium carbide coating with high hardness and excellent interfacial bond strength on GCr15. The coating is composed of Nb2C, NbC, and α-Fe phases. The volume fraction of niobium carbide (Nb2C and NbC) phases reaches 93%. Along the direction of coating thickness, the grain morphology of niobium carbide changes from equiaxed (Nb2C) to columnar (NbC), and then to equiaxed (NbC), presenting a gradient microstructure. The coating/substrate interface displays an excellent macro/micro interface. The formation of the gradient microstructure is attributed to the nucleation-growth process controlled by the carbon concentration gradient diffusion. The novel gradient coating can simultaneously achieve superhardness (20.2 ± 0.3 GPa) and excellent bond strength (>210 ± 20 MPa). The excellent bond strength is mainly attributed to the in-situ formation of the coating and the gradient microstructures. The tensile test results show that the fracture mechanism of the niobium carbide coating on GCr15 is mainly a brittle fracture of niobium carbide coating and a small amount of coating debonding

Triflumizole Induces Developmental Toxicity, Liver Damage, Oxidative Stress, Heat Shock Response, Inflammation, and Lipid Synthesis in Zebrafish

Triflumizole (TFZ) toxicity must be investigated in the aquatic environment to understand the potential risks to aquatic species. Accordingly, the adverse effects of TFZ exposure in zebrafish were investigated. Results demonstrate that, after TFZ exposure, the lethal concentration 50 (LC50) in 3 d post-fertilization (dpf) embryos and 6 dpf larvae were 4.872 and 2.580 mg/L, respectively. The development (including pericardium edema, yolk sac retention, and liver degeneration) was apparently affected in 3 dpf embryos. Furthermore, the alanine aminotransferase (ALT) activity, superoxide dismutase (SOD) activity, catalase (CAT) activity, and malondialdehyde (MDA) content in 6 dpf larvae were significantly increased. Additionally, the expression of heat shock response genes (including hsp70, grp78, hsp90, and grp94), inflammatory genes (including p65-nfκb, il-1β, and cox2a), and lipid synthetic genes (including srebp1, fas, acc, and ppar-γ) in 3 dpf embryos was significantly increased, which was also partially observed in the intestinal cell line form Pampus argenteus. Taken together, TFZ could affect the development of zebrafish, accompanied by disturbances of oxidative stress, heat shock response, inflammation, and lipid synthesis. Our findings provide an original insight into the potential risks of TFZ to the aquatic ecosystem

Experimental investigations on B2O3-Al2O3-SiO2 glass-ceramics with different K2O/Na2O ratios for sealing to Kovar alloy

This work studied the effects of the K2O/Na2O ratio on the viscosity of B2O3-Al2O3-SiO2 parent glass and the microstructure, physical, and chemical properties of the resulting glass-ceramics after heat treatment. Additionally, the effect of sealing temperatures on the sealing strength of glass-ceramics-to-Kovar was studied. The results show that the viscosity of parent glass increases with the increase in the R (R=n(K2O)/[n(Na2O)+n(K2O)]) value, and the viscous activation energy of BAS parent glass is about 262.65–293.85 KJ/mol. After heat treatment, the parent glass precipitates the main crystalline phase of Al0.52Zr0.48O1.74 (PDF#53–0294) and ZrO2 (PDF#37–1484). As the R value gradually increases, the thermal expansion coefficient of glass-ceramics initially decreases before increasing within the range of 44.74×10−7 to 52.29×10−7 ℃−1. The density follows a similar trend, fluctuating between 2.40 and 2.45 g/cm3. Meanwhile, the resistivity of the glass-ceramics steadily increases from 1×1012.07 to 1×1014.82 Ω·cm. Moreover, the resistivity of GcN-3 (R=1/2) sample remains excellent at high temperatures, maintaining 3.94×109 Ω·cm at 600 ℃. Subsequently，the BAS glass-ceramics sample GcN-3 (R=1/2) was sealed with Kovar alloy at temperatures range from 930 to 970℃. With the increasing of sealing temperature, the sealing strength increased from 0.51 to 2.10 MPa. In the process of sealing, with the increase of temperature, the iron in the Kovar alloy and the silicon in the glass-ceramics diffused to produce effective sealing and formed different sealing layers. The sealing area was observed to consist of four distinct regions: the matrix alloy, the alloy iron-deficiency area, the iron-rich glass-ceramics and the matrix glass-ceramics