Effects of Ion Irradiation and Temperature on Mechanical Properties of GaN Single Crystals under Nanoindentation.

Understanding the impact of irradiation and temperature on the mechanical properties of GaN single crystals holds significant relevance for rational designs and applications of GaN-based transistors, lasers, and sensors. This study systematically investigates the influence of C-ion irradiation and temperature on pop-in events, hardness, Young's modulus, and fracture behavior of GaN single crystals through nanoindentation experiments. In comparison with unirradiated GaN samples, the pop-in phenomenon for ion-irradiated GaN samples is associated with a larger critical indentation load, which decreases with increasing temperature. Both unirradiated and ion-irradiated GaN samples exhibit a decline in hardness with increasing indentation depth, while Young's moduli do not exhibit a clear size effect. In addition, intrinsic hardness displays an inverse relationship with temperature, and ion-irradiated GaN single crystals exhibit greater intrinsic hardness than their unirradiated counterparts. Our analysis further underscores the significance of Peierls stress during indentation, with this stress decreasing as temperature rises. Examinations of optical micrographs of indentation-induced fractures demonstrate an irradiation embrittlement effect. This work provides valuable insights into the mechanical behavior of GaN single crystals under varying irradiation and temperature conditions.

Carbyne Nanocrystal: One-Dimensional van der Waals Crystal.

In terms of carbon-atom hybridization, well-established forms of carbon are the first carbon diamond with three-dimensional sp3-hybridized carbon atoms and the second carbon graphite with two-dimensional sp2-hybridized carbon atoms which have been known and utilized for millennia. Sequentially, there is the third carbon, i.e., carbyne with one-dimensional (1D) sp-hybridized carbon atoms, which would result in an allotrope of carbon. Here, we demonstrate that carbyne nanocrystals (CNCs) are 1D van der Waals crystals (1D-vdWCs) composed of 1D carbon chains with sp-hybridized carbon atoms, and van der Waals action occurs between carbon chains based on an atomic insight into 1D sp-carbon chains. CNCs are synthesized by laser ablation in liquids, and the relevant spectroscopic analyses confirm that CNCs are composed of 1D carbon chains with the alternating carbon-carbon single and triple bonds. The crystal structure of CNCs is determined by X-ray diffraction, transmission electron microscopy (TEM), including selective electron diffraction (SAED), high-resolution TEM (HRTEM), and scanning TEM (STEM) and the corresponding simulations. SAED and HRTEM images reveal the translational symmetry of CNCs, and STEM images show the specific position of the carbon chain in CNCs and the arrangement of atoms on the carbon chain. Experimental data are in good agreement with the simulations, which demonstrate that CNCs are 1D-vdWCs with a hexagonal lattice in which the 1D carbon chain has a kinked structure consisting of an alternating carbon-carbon single bond and a triple bond of eight carbon atoms in a cycle. These findings bring out an emerging era of the third carbon carbyne.

Molecular Luminescence of White Carbon.

Four-color emission modulated by the molecular chain length from white carbon (carbyne crystals) is observed. It is also established that a carbyne molecule with four carbon atoms is the basic unit or building block to construct carbyne crystals, where the chain length of the carbyne molecule in the synthesized carbyne crystals follows the rule of 4n (n = 1, 2, 3, …).

Design, synthesis and inhibitory activity against human dihydroorotate dehydrogenase (hDHODH) of 1,3-benzoazole derivatives bearing amide units.

A series of 1,3-benzoazole derivatives possessing amide moieties were designed, synthesized and evaluated as inhibitors against human dihydroorotate dehydrogenase (hDHODH). Compounds A11, A14 and A26 exhibited good to excellent activities against hDHODH at the concentration of 10µM. In particular, compound A14 displayed an IC50 value of 0.178µM with 2-fold preference over A771726. The result implied that a proper degree of steric size and electron density of the C-6 amide moiety was necessary to retain the inhibitory activity of the synthesized compounds.

High glucose induces autophagy of MC3T3-E1 cells via ROS-AKT-mTOR axis.

In the present study, we investigate the function of ROS-AKT-mTOR axis on the apoptosis, proliferation and autophagy of MC3T3-E1 cells, and the proliferation of MC3T3-E1 cells after autophagy inhibition under high glucose conditions. MC3T3-E1 cells cultured in vitro were divided into the following groups: normal control group, N-acetylcysteine (NAC) group, 11.0 mM high glucose group, 11.0 mM high glucose + NAC group, 22.0 mM high glucose group, 22.0 mM high glucose + NAC group, CQ group, 22.0 mM high glucose + CQ group, 3-MA group and 3-MA + 22.0 mM high glucose group. ROS production was measured by DCFH-DA fluorescent probe. Cell proliferation was measured by MTT assay. Cells in different groups were stained with Annexin V-FITC/PI, and then apoptosis rate was detected by flow cytometry. Nucleus morphology was observed under fluorescence microscope after being incubated with Honchest33258. Protein expression was measured using Western blotting and immunofluorescence. Cell apoptosis and proliferation in high glucose group were increased and decreased, respectively, in a dose-dependent manner. Autophagy was significantly induced in high glucose group, even though different concentration of glucose induced autophagy in different stages of autophagy. ROS production in MC3T3-E1 cells was remarkably increased in high glucose group, but not in a dose-dependent manner. NAC, as an antioxidant, reduced ROS production and ameliorated cell apoptosis, proliferation abnormity and autophagy caused by high glucose. Expression of p-AKT and p-mTOR proteins were dramatically decreased in high glucose group, and NAC reversed their expression. In addition, 3-MA, an inhibitor of autophagy, significantly decreased the proliferation of MC3T3-E1 cells. When cocultured with 22.0 mM glucose that induced autophagy, proliferation of MC3T3-E1 cells was not affected compared to 22.0 mM high glucose group. Our present findings reveal that high glucose affects apoptosis, proliferation and autophagy of MC3T3-E1 cells through ROS-AKT-mTOR axis. In addition, autophagy inhibition does not affect the proliferation of MC3T3-E1 cells under high glucose conditions.

MicroRNA-335-5p inhibits osteoblast apoptosis induced by high glucose.

Diabetic osteoporosis represents a serious health condition with increasing incidence. Previous studies have shown that microRNA (miR)-335-5p is highly expressed in MC3T3-E1 osteoblasts and promotes their differentiation via downregulating the expression of dickkopf­1 (DKK1). The present study investigated the effects of miR­335­5p on apoptosis of osteoblasts induced by high glucose (HG), as well as the underlying molecular mechanisms. MC3T3­E1 osteoblasts were transfected with miR­335­5p mimics or control miR and cultured under HG conditions for seven days. Reverse­transcription PCR and showed that, compared with the control group, the expression levels of miR­335­5p were significantly downregulated in the HG group. However, no significant differences were observed in the mRNA expression levels of DKK1 between these groups. Furthermore, flow cytometric analysis showed that the apoptotic rate was increased by >2­fold in the HG group compared with that in the control group, while miR­335­5p overexpression significantly decreased the apoptotic rate in these model cells by ~40%. In addition, western blot analysis revealed that the protein expression levels of DKK1 and caspase­3 were significantly elevated in the HG group, which was significantly inhibited by overexpression of miR­335­5p. These results may indicate that miR­335­5p overexpression inhibited HG­induced apoptosis of MC3T3­E1 osteoblasts through decreasing the protein expression levels of DKK1. The results of the present study suggested that miR­335­5p may represent a potential target for the treatment of diabetic osteoporosis.

Carbyne with finite length: The one-dimensional sp carbon.

Carbyne is the one-dimensional allotrope of carbon composed of sp-hybridized carbon atoms. Definitive evidence for carbyne has remained elusive despite its synthesis and preparation in the laboratory. Given the remarkable technological breakthroughs offered by other allotropes of carbon, including diamond, graphite, fullerenes, carbon nanotubes, and graphene, interest in carbyne and its unusual potential properties remains intense. We report the first synthesis of carbyne with finite length, which is clearly composed of alternating single bonds and triple bonds, using a novel process involving laser ablation in liquid. Spectroscopic analyses confirm that the product is the structure of sp hybridization with alternating carbon-carbon single bonds and triple bonds and capped by hydrogen. We observe purple-blue fluorescence emissions from the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital of carbyne. Condensed-phase carbyne crystals have a hexagonal lattice and resemble the white crystalline powder produced by drying a carbyne solution. We also establish that the combination of gold and alcohol is crucial to carbyne formation because carbon-hydrogen bonds can be cleaved with the help of gold catalysts under the favorable thermodynamic environment provided by laser ablation in liquid and because the unique configuration of two carbon atoms in an alcohol molecule matches the elementary entity of carbyne. This laboratory synthesis of carbyne will enable the exploration of its properties and applications.

Electronic Reconstruction of α-Ag2WO4 Nanorods for Visible-Light Photocatalysis.

α-Ag2WO4 (AWO) has been studied extensively due to its H2 evolution and organic pollution degradation ability under the irradiation of UV light. However, the band gap of AWO is theoretically calculated to be 3.55 eV, resulting in its sluggish reaction to visible light. Herein, we demonstrated that, by using the electronic reconstruction of AWO nanorods upon a unique process of laser irradiation in liquid, these nanorods performed good visible-light photocatalytic organics degradation and H2 evolution. Using commercial AWO powders as the starting materials, we achieved the electronic reconstruction of AWO by a recrystallization of the starting powders upon laser irradiation in liquid and synthesized AWO nanorods. Due to the weak bond energy of AWO and the far from thermodynamic equilibrium process created by laser irradiation in liquid, abundant cluster distortions, especially [WO6] cluster distortions, are introduced into the crystal lattice, the defect density increases by a factor of 2.75, and uneven intermediate energy levels are inset into the band gap, resulting in a 0.44 eV decrease of the band gap, which modified the AWO itself by electronic reconstruction to be sensitive to visible light without the addition of others. Further, the first-principles calculation was carried out to clarify the electronic reconstruction of AWO, and the theoretical results confirmed the deduction based on the experimental measurements.

A novel colorimetric fluoride sensor based on a semi-rigid chromophore controlled by hydrogen bonding.

A novel semi-rigid latent chromophore E1, containing an amide subunit activated by an adjacent semi-rigid intramolecular hydrogen-bonding (IHB) unit, was designed for the detection of fluoride ion by the 'naked-eye' in CH3CN. Comparative studies on structural analogs (E2, E3, and E4) provided significant insight into the structural and functional role of the amide N-H and IHB segment in the selective recognition of fluoride ions. The deprotonation of the amide N-H followed by the enhancement of intramolecular charge transfer (ICT) induced the colorimetric detection of E1 for fluoride ion.

Insulin glargine effectively achieves glycemic control and improves insulin resistance in patients with early type 2 diabetes that exhibit a high risk for cardiovascular disease.

In the present study, the clinical efficacy and safety of administering insulin glargine to early type 2 diabetes (T2D) mellitus patients with a high risk for cardiovascular disease were assessed. A total of 42 early T2D patients at a high risk for cardiovascular disease were randomly divided into an insulin-glargine group and a standard-care group. The patients in the insulin-glargine group received oral antidiabetic agents plus glargine once a day via a subcutaneous injection. The patients in the standard-care group were administered oral antidiabetic agents according to the diabetic treatment guidelines. The median follow-up period was 6.4 years. Comparisons were made between the two groups with regard to levels of plasma glucose, glycosylated hemoglobin (HbA1c) and plasma lipids, the homeostasis model assessment-insulin secretion index (HOMA-ß) and HOMA-insulin resistance index (HOMA-IR), as well as the incidence of hypoglycemia, adverse cardiovascular events and body mass index (BMI). The fasting plasma glucose level in the insulin-glargine group was significantly lower than that observed in the standard-care group. However, the levels of 2-h postprandial glucose, HbA1c and plasma lipids, as well as the BMI, were similar when comparing the two groups. Although the level of the HOMA-ß did not differ between the two groups, the level of HOMA-IR in the insulin-glargine group was significantly lower than that observed in the standard-care group. During the follow-up period, the incidence of hypoglycemia in the insulin-glargine group was significantly higher when compared with the standard-care group, however, no significant difference in the incidence of adverse cardiovascular events was observed. Therefore, the results of the present study indicated that insulin glargine may effectively achieve glycemic control and improve insulin resistance without increasing the risk for cardiovascular events in early T2D patients that were considered to be at a high risk for cardiovascular disease.

Ferromagnetism and semiconducting of boron nanowires.

More recently, motivated by extensively technical applications of carbon nanostructures, there is a growing interest in exploring novel non-carbon nanostructures. As the nearest neighbor of carbon in the periodic table, boron has exceptional properties of low volatility and high melting point and is stronger than steel, harder than corundum, and lighter than aluminum. Boron nanostructures thus are expected to have broad applications in various circumstances. In this contribution, we have performed a systematical study of the stability and electronic and magnetic properties of boron nanowires using the spin-polarized density functional calculations. Our calculations have revealed that there are six stable configurations of boron nanowires obtained by growing along different base vectors from the unit cell of the bulk α-rhombohedral boron (α-B) and ß-rhombohedral boron (ß-B). Well known, the boron bulk is usually metallic without magnetism. However, theoretical results about the magnetic and electronic properties showed that, whether for the α-B-based or the ß-B-based nanowires, their magnetism is dependent on the growing direction. When the boron nanowires grow along the base vector [001], they exhibit ferromagnetism and have the magnetic moments of 1.98 and 2.62 µB, respectively, for the α-c [001] and ß-c [001] directions. Electronically, when the boron nanowire grows along the α-c [001] direction, it shows semiconducting and has the direct bandgap of 0.19 eV. These results showed that boron nanowires possess the unique direction dependence of the magnetic and semiconducting behaviors, which are distinctly different from that of the bulk boron. Therefore, these theoretical findings would bring boron nanowires to have many promising applications that are novel for the boron bulk.

[Characterization of the changes in comparative genomic hybridization in esophageal cancer patients with family history].

OBJECTIVE: To characterize the profile of chromosomal imbalances in esophageal cancer (EC) with or without family history in Linzhou, Henan Province of China. METHODS: Comparative genomic hybridization (CGH) was used to examine 13 cases with positive family history of EC and 32 cases with negative family history of EC. RESULTS DNA copy number gains on chromosome 10q was observed only in the cases with postivie family history of EC (30%), and none in cases with a negative family history (P<0.05). DNA copy number losses on chromosome 15q were significantly higher in cases with postivie family history (38% vs 6%, P<0.05). The frequency of DNA copy number gains in 3q, 5p, 7p, 8q and DNA copy number losses in 3p, 19q, 9q were similar in the two groups (both beyond 20%) (P>0.05). CONCLUSIONS: Frequent DNA copy number gains on chromosome 10q and losses on chromosome 15q in EC casers with postivie family history indicate that these chromosome sites may harbor the genes related to high susceptibility to EC. Such chromosomal sites as 3q, 5p, 7p, 8q, 3p, 19q, and 9q may contain important genes related with the environmental risk factors of esophageal carcinogenesis.

The electronic structure evolution of DNA during its conformation transition process.

We combined classical molecular dynamics (MD) simulation with ab initio calculations to study the electronic structure evolution of DNA during its conformation transition process. By using MD simulation, we obtained the conformation transition trajectory of an oligonucleotide poly(dC)-poly(dG), from which we selected a series of representative conformations and then performed ab initio calculations for these conformations to reveal their electronic structures. Counterintuitively, the results indicate that during the conformation transition process of DNA, thermal fluctuation plays a more important role than global conformation parameters in affecting the electronic structure of DNA.

From pure C(60) to silicon carbon fullerene-based nanotube: an ab initio study.

The energetics, geometrical, and electronic properties of the silicon carbon fullerene-based materials, obtained from C(60) by replacing 12 carbon atoms of the C(60) cage with silicon atoms, are studied based on ab initio calculations. We have found that, of the two C(48)Si(12) isomers obtained, the one with the carbon atoms and the silicon atoms located in separated region, i.e., with a phase-separated structure is more stable. Fullerene-based C(36)Si(24) cluster, C(36)Si(24)-C(36)Si(24) dimer, and the nanotube constructed from the clusters are then studied. The calculations on the electronic properties of these silicon carbon fullerene-based nanomaterials demonstrate that the energy gaps are greatly modified and show a decreasing trend with increasing the size of the clusters. The silicon carbon fullerene-based nanotube has a narrow and direct energy band gap, implying that it is a narrow gap semiconductor and may be a promising candidate for optoelectronic devices.

The electronic structure of a single-walled aluminosilicate nanotube.

The geometric structure and electronic structure of an imogolite nanotube have been studied using density functional theory (DFT). The calculation results indicate that the deformation of the material leads to structural electric charges on the tube wall. This hydrous aluminosilicate single-walled nanotube is a wide gap semiconductor with a direct band gap, E(g)∼3.67 eV at the Γ point, which may be promising for application in optoelectronic devices. In conjunction with the DFT calculations, molecular dynamics simulations based on empirical potentials are also performed to evaluate the mechanical properties of this material.