High-quality planar light emitting diode formed by induced two-dimensional electron and hole gases.

A high-quality planar two-dimensional p-i-n light emitting diode in an entirely undoped GaAs/AlGaAs quantum well has been fabricated by using conventional lithography process. With twin gate design, two-dimensional electron and hold gases can be placed closely on demand. The electroluminescence of the device exhibit high stability and clear transition peaks so it is promising for applications on electrically-driven single photon sources.

Low PTEN expression and overexpression of phosphorylated AktSer473 and AktThr308 are associated with poor overall survival in upper tract urothelial carcinoma.

The PI3K/Akt signaling pathway serves an essential role in various cellular processes, including cell growth, survival, cell motility, angiogenesis and cell metabolism. Loss of PTEN expression and hyperactivation of Akt can result in tumorigenesis. Previous studies observed expression of the Akt protein and absence of the PTEN protein in bladder cancer and non-small cell lung carcinoma tissues. The aim of the present study was to evaluate the expression status and prognostic value of PTEN and the PI3K/Akt signaling pathway in Taiwanese patients with upper tract urothelial carcinoma (UTUC). Archival formalin-fixed, paraffin-embedded (FFPE) tissues from 65 UTUC cases were stained via immunohistochemistry for PTEN, phosphorylated (p)Akt serine (Ser)473 and pAkt threonine (Thr)308. The expression levels of each protein were significantly correlated with clinicopathological parameters. PTEN, pAktSer473 and pAktThr308 protein expression levels were higher in adjacent normal tissues compared with those in tumor tissues. Cytoplasmic PTEN protein expression levels were lower in high-stage tumors compared with those in low-stage tumors, and nuclear and cytoplasmic pAktThr308 protein expression levels were higher in high-grade tumors compared with those in low-grade tumors. Univariate analysis showed that high pathological tumor stage (pT2-4) [P=0.01; hazard ratio (HR)=3.40; 95% confidence interval (CI), 1.34-8.60], metastatic status (P=0.003; HR=3.55, 95% CI, 1.55-8.11), low cytoplasmic PTEN protein expression levels (P=0.016; HR=3.14; 95% CI, 1.24-7.95) and high cytoplasmic pAktSer473 protein expression levels (P=0.019, HR=2.71, 95% CI, 1.18-6.21) were predictive of poor overall survival. However, only metastatic status (P=0.031; HR=2.73; 95% CI, 1.10-6.78), low cytoplasmic PTEN protein expression levels (P=0.017; HR=3.29; 95% CI, 1.24-8.73) and high cytoplasmic pAktSer473 protein expression levels (P=0.027; HR=2.64; 95% CI, 1.12-6.23) remained significant in the multivariate analysis. Kaplan-Meier survival analysis showed that high T stage, metastasis, low expression levels of cytoplasmic PTEN protein and high expression levels of cytoplasmic pAktSer473 protein were significantly associated with poor survival (P=0.006, 0.001, 0.011 and 0.014, respectively). Co-expression of PTENlow/pAktSer473/high and pAktThr308/high phenotypes was associated with a less favorable overall survival (P=0.001). Overall, the present findings demonstrated that low expression levels of PTEN and high expression levels of pAktSer473 and pAktThr308 were predictors for poor overall survival in patients with UTUC.

Structural, Photophysical, and Electronic Properties of CH3NH3PbCl3 Single Crystals.

Methylammonium lead chloride (CH3NH3PbCl3 or MAPbCl3) single crystals were fabricated using the inverse temperature crystallization method, and their structural, photophysical, and electronic characteristics were studied using temperature dependent optical spectroscopy, X-ray diffraction (XRD), current-voltage, and Hall measurements. The changes in absorption and photoluminescence properties accompanied with structural changes in crystal lattice were studied within a broad temperature range of 300-20 K. XRD investigations reveal that phase changes took placed around 180 K and 175 K. At a temperature below 170 K, two different crystallographic phases were found to co-exist in the photoluminescence spectra. An asymmetric line shape with broad and weak shoulders near the absorption edges was observed in all of the major PL peaks. The weak shoulders are attributed to the missing chloride atoms on the crystal surface. The photoluminescence intensity of the crystals was strongly influenced by the environment, thereby indicating that the carrier recombination is affected by the physical desorption/absorption of gas molecules at the crystal surface. Moreover, vibronic replicas in the photoluminescence spectra at low temperature were observed for the first time. The origins of these replicas are attributed to the coupling between the vibrational/librational motions of the organic cations and the photoexcited electrons. Finally, the Hall and current-voltage measurements confirm that the crystal is an n-type semiconductor with a carrier concentration of ~2.63 × 1011 cm-3, a mobility of 4.14 cm2/V•s, and a conductivity of 1.8 × 10-8 Ω-1 cm-1 under dark and room temperature conditions.

Effect of Metal Ions on Hybrid Graphite-Diamond Nanowire Growth: Conductivity Measurements from a Single Nanowire Device.

Novel Cd2+ ions mediated reproducible hybrid graphite-diamond nanowire (G-DNWs; Cd2+-NDS1 NW) growth from 4-Amino-5-phenyl-4H-1,2,4-triazole-3-thiol (S1) functionalized diamond nanoparticles (NDS1) via supramolecular assembly is reported and demonstrated through TEM and AFM images. FTIR, EDX and XPS studies reveal the supramolecular coordination between functional units of NDS1 and Cd2+ ions towards NWs growth. Investigations of XPS, XRD and Raman data show the covering of graphite sheath over DNWs. Moreover, HR-TEM studies on Cd2+-NDS1 NW confirm the coexistence of less perfect sp² graphite layer and sp³ diamond carbon along with impurity channels and flatten surface morphology. Possible mechanisms behind the G-DNWs growth are proposed and clarified. Subsequently, conductivity of the as-grown G-DNWs is determined through the fabrication of a single Cd2+-NDS1 NW device, in which the G-DNW portion L2 demonstrates a better conductivity of 2.31 × 10-4 mS/cm. In addition, we investigate the temperature-dependent carrier transport mechanisms and the corresponding activation energy in details. Finally, comparisons in electrical resistivities with other carbon-based materials are made to validate the importance of our conductivity measurements.

[Expression of NR1 mRNA of NMDA receptor by gastrodine on hypoxia injury in cultured rat cerebral cortical neurons].

OBJECTIVE: To investigate the effect of gastrodine on the expression of NR1 mRNA of NMDA receptor in cultured rat cerebral cortical neurons injury induced by hypoxia. METHOD: The injury models of cultured rat cerebral cortical neurons was made by hypoxia and hypoglucose. The concentration of 13, 26, 52 mg x L(-1) of gastrodine was respectively added to the injured cells. The R-PCR technique was used to study the expression of NR1 mRNA of NMDA receptor. RESULT: The expression of NR1 mRNA increased markedly in hypoxia and hypoglucose injured cells, the increased expression can be weakened by gastrodine, more significant effect was found in the concentration of 26 mg x L(-1) 52 mg x L(-1). CONCLUSION: Gastrodine may act as a neuro - protector by weakening the expression of NR1 mRNA in cultured rat cerebral cortical neurons injury induced by hypoxia and hypoglucose.

Structural and Photophysical Properties of Methylammonium Lead Tribromide (MAPbBr3) Single Crystals.

The structural and photophysical characteristics of MAPbBr3 single crystals prepared using the inverse temperature crystallization method are evaluated using temperature-dependent X-ray diffraction (XRD) and optical spectroscopy. Contrary to previous research reports on perovskite materials, we study phase transitions in crystal lattice structures accompanied with changes in optical properties expand throughout a wide temperature range of 300-1.5 K. The XRD studies reveal several phase transitions occurred at ~210 K, ~145 K, and ~80 K, respectively. The coexistence of two different crystallographic phases was observed at a temperature below 145 K. The emission peaks in the PL spectra are all asymmetric in line shape with weak and broad shoulders near the absorption edges, which are attributed to the Br atom vacancy on the surface of the crystals. The time-resolved PL measurements reveal the effect of the desorption/adsorption of gas molecules on the crystal surface on the PL lifetimes. Raman spectroscopy results indicate the strong interplays between cations and different halide atoms. Lastly, no diamagnetic shift or split in emission peaks can be observed in the magneto-PL spectra even at an applied magnetic field up to 5 T and at a temperature as low as 1.5 K.

An Affordable Wet Chemical Route to Grow Conducting Hybrid Graphite-Diamond Nanowires: Demonstration by A Single Nanowire Device.

We report an affordable wet chemical route for the reproducible hybrid graphite-diamond nanowires (G-DNWs) growth from cysteamine functionalized diamond nanoparticles (ND-Cys) via pH induced self-assembly, which has been visualized through SEM and TEM images. Interestingly, the mechanistic aspects behind that self-assembly directed G-DNWs formation was discussed in details. Notably, above self-assembly was validated by AFM and TEM data. Further interrogations by XRD and Raman data were revealed the possible graphite sheath wrapping over DNWs. Moreover, the HR-TEM studies also verified the coexistence of less perfect sp2 graphite layer wrapped over the sp3 diamond carbon and the impurity channels as well. Very importantly, conductivity of hybrid G-DNWs was verified via fabrication of a single G-DNW. Wherein, the better conductivity of G-DNW portion L2 was found as 2.4 ± 1.92 × 10-6 mS/cm and revealed its effective applicability in near future. In addition to note, temperature dependent carrier transport mechanisms and activation energy calculations were reported in details in this work. Ultimately, to demonstrate the importance of our conductivity measurements, the possible mechanism behind the electrical transport and the comparative account on electrical resistivities of carbon based materials were provided.

Low temperature and high magnetic field spectroscopic ellipsometry system.

We report on the design and implementation of a spectral ellipsometer at near-infrared wavelength (700-1000 nm) for samples placed in high magnetic fields (up to 14 T) at low temperatures (~4.2 K). The main optical components are integrated in a probe, which can be inserted into a conventional long-neck He dewar and has a very long free-space optical path (~1.8 m×2). A polarizer-sample-(quarter-wave plate)-rotating analyzer configuration was employed. Two dielectric mirrors, one before and one after the sample in the optical path, helped to reflect the light back to the analyzer and a two-axis piezo-driven goniometer under the sample holder was used to control the direction of the reflected light. Functional test results performed on an intrinsic GaAs wafer and analysis on the random error of the system are shown. We obtained both amplitude and phase ellipsometric spectra simultaneously and observed helicity transformation at energies near the GaAs exciton transitions in the phase spectra. Significant shifts of them induced by magnetic fields were observed and fitted with a simple model. This system will allow us to study the collective magneto-optical response of materials and spatial dispersive exciton-polariton related problems in high external magnetic fields at low temperatures.

Selective reduction of anti-Helicobacter pylori IgG subclass antibody in gastric carcinoma.

BACKGROUND: Epidemiological studies have demonstrated strong links between Helicobacter pylori infection and gastric adenocarcinoma. Recent studies suggest that cell-mediated immunity influences the outcome of infection, including the development of gastric adenocarcinoma. The T-cell response can be characterized in terms of the secreted cytokine profile, which in turn influences the B-cell response including the balance of IgG subclass antibody. METHODS: Serum anti-H. pylori IgG, IgG1 and IgG2 antibodies were studied by ELISA in subjects with benign gastric diseases, gastric dysplasia and gastric adenocarcinoma. RESULTS: The distribution patterns of IgG subclass anti-H. pylori antibody varies significantly between H. pylori-linked benign and malignant disease in subjects infected with H. pylori. Significantly lower IgG2 levels were found in subjects with gastric adenocarcinoma compared with those with reflux esophagitis, chronic gastritis, gastric ulcer, and peptic ulcer, while IgG1 antibody remained at similar levels in both benign and malignant disease. A limited study of seropositive subjects with premalignant change was consistent with the fall in IgG2 antibody pre-dating malignant change, although pre-eradication results are needed to validate these data. CONCLUSIONS: These studies indicate that subjects with low levels of IgG2 anti-H. pylori antibody are at risk of gastric adenocarcinoma, and that the previously described linkage between gastric adenocarcinoma and low total IgG antibody does not simply reflect reduced gastric colonization. The diagnostic value of this assay for pre-endoscopy screening is attractive.