Search

The structural properties and the spin states of vacancies in ion implanted silicon carbide samples are analyzed by experimental measurements along with first-principles calculations. Different types and dosages of ions (N+, O+, and B+) were implanted in the 4H-silicon carbide single crystal. The Raman spectra, positron annihilation spectroscopy, and magnetization-magnetic field curves of the implanted samples were measured. The fitting results of magnetization-magnetic field curves reveal that samples implanted with 1×1016cm-2 N+ and O+ ions generate paramagnetic centers with various spin states of J = 1 and J=0.7, respectively. While for other implanted specimens, the spin states of the paramagnetic centers remain unchanged compared with the pristine sample. According to the positron annihilation spectroscopy and first-principles calculations, the change in spin states originates from the silicon vacancy carrying a magnetic moment of 3.0 μB in the high dosage N-implanted system and 2.0 μB in the O-doped system. In addition, the ratio of the concentration of implanted N ions and silicon vacancies will affect the magnetic moment of VSi. The formation of carbon vacancy which does not carry a local magnetic moment in B-implanted SiC can explain the invariability in the spin states of the paramagnetic centers. These results will help to understand the magnetic moments of vacancies in ion implanted 4H-SiC and provide a possible routine to induce vacancies with high spin states in SiC for the application in quantum technologies and spintronics. [ABSTRACT FROM AUTHOR]

Heavy metal contaminated wastewater is difficult to treat, and trace amounts of heavy metals can produce toxic effects. In order to provide a more reliable basis for controlling heavy metal pollution, modified carbonized straw was used to adsorb Cr6+ in this study, and the optimal adsorption conditions and adsorption effects of Cr6+ were studied. Finally, the adsorption kinetics and adsorption activation thermodynamics were analyzed and studied. The results showed that the iodine adsorption value of carbonized wheat straw modified using FeCl2 activation method was the highest at 1161.15 mg/g. The response surface method can be used to optimize the adsorption conditions of Cr6+ adsorbed by modified carbonized straw and predict the optimal conditions for Cr6+ adsorption. Experiments showed that the actual value was in agreement with the predicted value, indicating that the response surface methodology was feasible to optimize the adsorption of Cr6+ by modified carbonized straw. In the kinetic analysis, the Elovich equation could better describe the adsorption of Cr6+ by modified carbonized wheat straw, and its fitting degree exceeded 0.91. In the analysis of thermodynamic parameters, ΔH > 0, ΔG < 0, indicating that the adsorption of Cr6+ by modified wheat straw was a spontaneous endothermic process. During the adsorption process, ΔS > 0, indicating that the adsorption of Cr6+ by modified carbonized wheat straw increased the disorder of the system. [ABSTRACT FROM AUTHOR]

β-SiC nanoparticles (NPs) were anchored onto the surface of reduced graphene oxide (RGO) by a facile solvothermal method. The characterization results of the novel RGO-SiC composites indicate an effective chemical interaction between the RGO sheets and β-SiC NPs. Moreover, methylene blue (MB) dye was employed as a model pollutant to evaluate the adsorption and photocatalytic ability of the composites. It is found that the content of RGO sheets can significantly tune the adsorption and photocatalytic activity of various composites with an optimal value of 3 wt%. The enhancement of photocatalytic activity can be attributed to the synergistic effect of the accelerated separation of photogenerated electron-hole pairs, and the enhanced absorption ability for dyes is mainly due to the RGO sheets which work as an excellent photocatalyst supporter and offer electrons channel to accept and transfer the photogenerated carriers from excited β-SiC NPs. [ABSTRACT FROM AUTHOR]

Objective: Bietti crystalline dystrophy (BCD) is a rare degenerative eye disease caused by mutations in the CYP4V2 gene, and Cyp4v3 is the murine ortholog to CYP4V2 . To better understand the molecular pathogenesis of this disease and to explore the potential treatment we have established a Cyp4v3 knock-out mouse model., Methods: Cyp4v3 -/- mice were generated by clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 in embryonic stem cells of C57BL/6J mice. Ocular morphologic characteristics were evaluated via fundus imaging, histologic analysis of rods and cones via immunofluorescence, and phalloidin stain to observe retinal pigment epithelium (RPE) in whole-mounts, electroretinogram (ERG) was also conducted to examine the retinal function., Results: The characteristic features of BCD recurred in the Cyp4v3 -/- mice, including retinal crystalline deposits, atrophy and degeneration of RPE cells, and ERG amplitude decline of dark and light adapted a- and b- wave; however, the immunofluorescence stain of rod and cone cells did not show obvious differences when compared with the wild type (WT) mice. In the early stage of the disease, no crystal-like deposits were found in the fundus, ERG detection of the retinal function did not find a significant decline, and the morphological structure and quantity of the neural retina and RPE did not change significantly. Crystalline deposits occurred and converged when the Cyp4v3 -/- mice at the end of 6 months, and the deposits disappeared when the Cyp4v3 -/- mice at the end of 12 months. The ERG amplitude started to decline when the Cyp4v3 -/- mice at the end of 6 months and deteriorated at the end of 12 months. The RPE cells of the 12-month old Cyp4v3 -/- mice showed irregular shape by phalloidin staining of F-actin. The Cyp4v3 -/- mice behaved normally and were viable and fertile when maintained under specific pathogen-free (SPF) housing conditions., Conclusion: Just like BCD patients, the disease progress of Cyp4v3 -/- mouse is correlated with the age, which provides a good model for pathogenesis and gene therapy study in the future. The atrophy and degeneration of RPE take the lead in progressing of the disease, but the mechanism is not clear yet.

Genomic imprinting is an important epigenetic mechanism that has vital effects on fetal growth and development. We observed the differences in four tissues (heart, spleen, liver, and kidney) from dead transgenic cloned goats using hematoxylin and eosin (H&E) staining. Eight imprinted genes in the tissues of dead transgenic cloned and normal goats were analyzed using reverse transcription polymerase chain reaction. H&E staining results from the abortion group indicated the lack of obvious morphological changes in heart and spleen tissues, while inflammatory cell infiltration and glomerular nephritis characteristics were observed in liver and kidney tissues, respectively. Compared to the control group, CDKN1C, H19, IGF2R, and SNRPN were significantly (P < 0.05) overexpressed in the heart tissue of the abortion group, while XIST was significantly reduced. In the liver tissues, CDKN1C and DLK1 expression decreased, while GNAS, H19, IGF2R, PEG3, and XIST expression increased significantly. In the spleen tissues, DLK1 expression increased, while GNAS, H19, IGF2R, PEG3, SNRPN, and XIST expression decreased. In the kidney tissues, CDKN1C, DLK1, GNAS, IGF2R, and PEG3 expression increased, while H19 and XIST expression decreased. The overall expression of imprinted genes was abnormal in different tissues of transgenic cloned goats, and the degree of abnormal genomic imprinting was more severe in the abortion group compared to the death and control groups. These results suggest that abnormal expression of imprinted genes may cause developmental defects in transgenic cloned goats. Moreover, abnormal epigenetic modifications may affect the reprogramming of transgenic donor cells.

Dairy goat is a good model for production of transgenic proteins in milk using somatic cell nuclear transfer (SCNT). However, animals produced from SCNT are often associated with lung deficiencies. We recently produced six transgenic cloned dairy goats harboring the human lactoferrin gene, including three live transgenic clones and three deceased transgenic clones that died from respiratory failure during the perinatal period. Imprinted genes are important regulators of lung growth, and may be subjected to faulty reprogramming. In the present study, first, microsatellite analysis, PCR, and DNA sequence identification were conducted to confirm that these three dead kids were genetically identical to the transgenic donor cells. Second, the CpG island methylation profile of the imprinted insulin-like growth factor receptor (IGF2R) gene was assessed in the lungs of the three dead transgenic kids and the normally produced kids using bisulfite sequencing PCR. In addition, the relative mRNA level of IGF2R was also determined by real-time PCR. Results showed that the IGF2R gene in the lungs of the dead cloned kids showed abnormal hypermethylation and higher mRNA expression levels than the control, indicating that aberrant DNA methylation reprogramming is one of the important factors in the death of transgenic cloned animals.

Mesenchymal stem cells derived from bone marrow (BMSCs) are a population of self-renewing multipotent cells that are capable of differentiating into various cellular lineages, and are widely employed in tissue engineering and cell therapy. Recently, clinical research involving BMSCs has become increasingly popular. In order to conduct appropriate research, it is first necessary to amplify large amounts of functional BMSCs in vitro. However, after several passages of expanding in vitro, the proliferation and differentiation potential of BMSCs gradually decline. To determine whether overexpression of Oct4 or Sox2 might prevent this decline, we transfected Oct4 or Sox2, which are essential for the pluripotency and self-renewal of embryonic stem cells, into BMSCs of Xiaomeishan porcine by a lentivirus. The results showed that overexpression of Sox2 or Oct4 BMSCs in culture media containing a basic fibroblast growth factor resulted in higher proliferation and differentiation compared to controls, suggesting that genetic modification of stemness-related genes is an efficient way to maintain the proliferation and differentiation potential of BMSCs.