Energy Transfer and Population Inversion in Heavy Metal Oxide Glasses Doped with Tm3+ and Tb3+

Emission properties and energy transfer of PbO–Bi₂O₃–Ga₂O₃–GeO₂ glasses codoped with Tm³⁺ and Tb³⁺ ions were investigated. The 1.48-μm emission due to the Tm³⁺:³H₄→³F₄ transition can be used to amplify the S-band (1460–1530-nm) signal light. With Tb³⁺ addition, the lifetime and emission intensity of the Tm³⁺:³F₄ level decreased sharply via the Tm³⁺:³F₄→Tb³⁺:⁷F_0,1,2 energy transfer. Population densities of the ³F₄ and ³H₄ levels in Tm³⁺ calculated from rate equations clearly verified that population inversion in Tm³⁺ ions became possible with as little as 0.1 mol% of Tb³⁺ addition.     

Default Bayesian Priors for Regression Models with First-Order Autoregressive Residuals

Abstract. The objective of this paper is to develop default priors when the parameter of interest is the autocorrelation coefficient in normal regression models with first-order autoregressive residuals. Jeffreys' prior as well as reference priors are found. These priors are compared in the light of how accurately the coverage probabilities of Bayesian credible intervals match the corresponding frequentist coverage probabilities. It is found that the reference priors have a definite edge over Jeffreys' prior in this respect. Also, the credible intervals based on these reference priors seem superior to similar intervals based on certain divergence measures.     

Protein Ligation-Assisted Reconstitution of Split HRP Fragments for Facile Production of HRP Fusion Proteins in E. coli

Horseradish peroxidase (HRP) is a pivotal biocatalyst for biosensor development and fine chemical synthesis. HRP proteins are mostly extracted and purified from the roots of horseradish because the solubility and productivity of recombinant HRP in bacteria are significantly low. In this study, we investigate the reconstitution system of split HRP fragments to improve its soluble expression levels in E. coli allowing the cost-effective production of bioactive HRPs. To promote the effective association between two HRP fragments (HRPn and HRPc), we exploit SpyTag-SpyCatcher chemistry, a versatile protein coupling method with high affinity and selectivity. Each HRP fragment was genetically fused with SpyTag and SpyCatcher, respectively, exhibiting soluble expression in the E. coli cytoplasm. The engineered split HRPs were effectively and irreversibly reconstituted into a biologically active and stable assembly that can catalyze intrinsic enzymatic reactions. Compared to the chaperone co-expression system, our approach shows that the production yield of soluble HRP is comparable, but the purity of the final product is relatively high. Therefore, our results can be applied to the high-yield production of recombinant HRP variants and other difficult-to-express proteins in bacteria without complex downstream processes.     

Soluble polyimides with trifluoromethyl pendent groups

Unsymmetrical and symmetrical diamine monomers containing trifluoromethyl groups, 2-trifluoromethyl-4,4′-diaminodiphenyl sulfide and 2,2′-bis(trifluoromethyl)-4,4′-diamino-diphenyl sulfide, were synthesized from 2-chloro-5-nitrobenzotrifluoride as a starting material in two steps, respectively. Diamine monomers were polymerized with PMDA, BPDA, BTDA, and ODPA using a solution imidization method with N-methyl-2-pyrrolidone as a solvent at 190 °C to obtain the corresponding polyimides. They had inherent viscosities that ranged from 0.54 to 0.71 dL/g in N-methyl-2-pyrrolidone at 30 °C. All of the synthesized polyimides showed good solubility in polar aprotic solvents and phenolic solvents regardless of the number of trifluoromethyl groups. The 5% weight loss temperatures of the polyimides are in the range of 534–561 °C in nitrogen, and 505–542 °C in air. The T_g values and the thermal expansion coefficients of these polymers are in the range of 234–325 °C and in the range of 47.4–63.2 ppm/°C, respectively. Also, all of the synthesized polyimides have relatively low refractive indices (around 1.6) and birefringence (below 0.36).     

Enhancement of fibroblastic proliferation from photoreactive starch with immobilized epidermal growth factor

Carboxymethyl starch was modified by the incorporation of an azidophenyl group to prepare photoreactive starch, and characterized by Fourier transform infrared reflectance (FT‐IR), proton nuclear magnetic resonance (¹H‐NMR), and ultraviolet (UV) spectroscopy. Photo‐irradiation immobilized the Az‐starch on a polystyrene plate and it was stably retained on the surface. The protein containing immobilized Az‐starch was also immobilized on a stripe micropatterned plate. UV irradiation time and Az‐starch concentration were used to alter the physical properties of Az‐starch and consequently control the rate of epidermal growth factor (EGF) release. The Az‐starch that released growth factor was not cytotoxic to 3T3‐L1 fibroblast cells, and the immobilized EGF maintained its activity and induced cellular proliferation in vitro. These results suggest that Az‐starch could be useful as a clinical synthetic material for medical applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of structural change of pitch on the thermal conductivity of epoxy‐based composites filled with heat‐treated pitch

Petroleum‐based pitches were used as filler materials to study the effects of heat‐treatment‐induced changes in pitch structure on the thermal conductivity of epoxy‐based composites. The heat treatment was performed in two steps: the first involved heating the pitch to 250 °C in order to remove the low‐molecular‐weight compounds from the pitch, and the second involved heating the pitch to either 430 or 450 °C. There was no significant difference in the curing behavior of the diglycidyl ether of bisphenol A (DGEBA)/pitch composites, regardless of the heat‐treatment temperature. However, the thermal conductivity of the DGEBA/pitch composites improved with increasing heat‐treatment temperature, and the epoxy composite prepared with pitch heat‐treated at 430 °C exhibited the maximum thermal conductivity. This can be attributed to structural changes in the pitch, such as the distance between adjacent planes (d‐spacing), crystallite height (L_c) and crystallite width (L_a). Although L_c of the pitch increased with increasing heat‐treatment temperature, the d‐spacings and L_a decreased. These results suggest that the heat treatment of the pitch led to a well‐stacked crystalline structure. However, compared with the pitch heat‐treated at 430 °C, that heat‐treated at 450 °C exhibited lower thermal conductivity in the DGEBA/pitch composite because of the low L_a, resulting in the loss of basal carbon as a consequence of in situ gasification, and pyrolysis of the low‐molecular‐weight compounds in the pitch. © 2013 Society of Chemical Industry     

Effect of sintering atmospheres on the densification behavior of CuO ceramics

In this study, the effect of oxygen partial pressure on the densification and the resultant microstructure change of CuO were examined. When CuO green bodies were heated up to 1100 °C for sintering in air, denser CuO samples were obtained than the samples sintered in oxygen. When the samples were kept at 1100 °C for a prolonged period of time, however, the densification of the sample in oxygen was accelerated whereas that of the sample in air was hindered. This is attributed to the phase transformation from CuO to Cu₂O which accompanies oxygen release during sintering in air. On the basis of the results, dense CuO samples could be obtained by switching the sintering atmosphere from air to oxygen at the suitable stage so that oxygen release by reduction could be suppressed.     

miR-22-3p and miR-30e-5p Are Associated with Prognosis in Cervical Squamous Cell Carcinoma

Alteration in expression of miRNAs can cause various malignant changes and the metastatic process. Our aim was to identify the miRNAs involved in cervical squamous cell carcinoma (SqCC) and metastasis, and to test their utility as indicators of metastasis and survival. Using microarray technology, we performed miRNA expression profiling on primary cervical SqCC tissue (n = 6) compared with normal control (NC) tissue and compared SqCC that had (SqC-M; n = 3) and had not (SqC-NM; n = 3) metastasized. Four miRNAs were selected for validation by qRT-PCR on 29 SqC-NM and 27 SqC-M samples, and nine metastatic lesions (ML-SqC), from a total of 56 patients. Correlation of miRNA expression and clinicopathological parameters was analyzed to evaluate the clinical impact of candidate miRNAs. We found 40 miRNAs differentially altered in cervical SqCC tissue: 21 miRNAs were upregulated and 19 were downregulated (≥2-fold, p < 0.05). Eight were differentially altered in SqC-M compared with SqC-NM samples: four were upregulated (miR-494, miR-92a-3p, miR-205-5p, and miR-221-3p), and four were downregulated (miR-574-3p, miR-4769-3p, miR-1281, and miR-1825) (≥1.5-fold, p < 0.05). MiR-22-3p might be a metastamiR, which was gradually further downregulated in SqC-NM > SqC-M > ML-SqC. Downregulation of miR-30e-5p significantly correlated with high stage, lymph node metastasis, and low survival rate, suggesting an independent poor prognostic factor.     

Optical band gap modulation by Mg-doping in In2O3(ZnO)3 ceramics

In this study, different amounts of Mg were doped in In₂O₃(Zn_1−xMg_xO)₃ and their thin films were grown by using the RF magnetron sputtering method. The optical and electrical characteristics of the films revealed that the lattice constant decreased while the optical band gap increased as the Mg content increased, showing an inverse proportional relationship with each other. Therefore, it was found that Mg doping in indium zinc oxide (IZO) is also effective for band gap modulation as it was reported in a Mg-doped ZnO system. When IZO thin films were grown in a more reducing ambient, the carrier concentration increased which resulted in the increase of band gap energy. This was explained due to the Burstein–Moss effect.     

Rheological and thermal properties of epoxy nanocomposites reinforced with alkylated multi‐walled carbon nanotubes

The effects of functionalized multi‐walled carbon nanotubes (MWCNTs) on thermal and chemorheological behaviors of an epoxy‐based nanocomposite system were investigated. Chemical functionalization of MWCNTs by acid modification (A‐MWCNTs) and chemical amidation (D‐MWCNTs) was confirmed using Fourier transform infrared spectroscopy and thermogravimetric analysis. It was found that the D‐MWCNTs had a significant effect on the chemorheological behaviors of the epoxy‐based nanocomposite. Compared to the epoxy/A‐MWCNT nanocomposite, the epoxy/D‐MWCNTs nanocomposite showed a significant increase in gel time, as obtained from isothermal rheology measurements. Also, the storage modulus of the diglycidylether of bisphenol F (DGEBF)/D‐MWCNTs nanocomposite was higher than that of the DGEBF/D‐MWCNTs nanocomposite and gradually increased with an increase of frequency. This could be interpreted by the relatively strongly interconnected structure of the D‐MWCNTs in the DGEBF epoxy resin, which arises from the functionalized alkyl groups of the D‐MWCNTs in dispersion phases with the DGEBF epoxy resin. Copyright © 2012 Society of Chemical Industry