Effect of Multi-Pass Power Spinning on Microstructure Homogenization and Mechanical-Property Strengthening of Ti2AlNb-Based Alloy Using Welded Tube Blank.

Long seamless tubes of Ti2AlNb-based alloys are difficult to manufacture through conventional forming methods. In this study, a multi-pass power spinning process was first utilized to fabricate thin-walled tube of Ti-22Al-24Nb-0.5Mo alloy using welded thick tube blank, assisted by on-line electro-magnetic induction heating to maintain high spinning temperature during the whole spinning process. After six-pass hot power spinning at 950 ± 30 °C, the microhardness difference of BM (base metal), HAZ (heat affect zone) and FZ (fusion zone) became much smaller, and the microhardness fluctuation ΔHV dropped to 32 from 122 of the as-welded joint due to the phase composition and microstructure homogenization. The grain size of B2 phase was refined to 0.4/0.6 µm from 2.7/10.8 µm of the as-received BM/FZ, respectively. Meanwhile, the B2 phase <111>B2//ND texture of the as-received rolled sheet weakened during multi-pass spinning due to recrystallization, which co-existed with <001>B2//ND texture in final pass. The ultimate tensile strength in axial/tangential direction was increased to 1245/1299 MPa from 1206/1010 MPa of the as-received rolled sheet, respectively, mainly due to the effect of fine grain strengthening. This study provides an effective way to manufacture high-performance tubular workpieces with low cost and high efficiency.

Chirality of Single-Handed Twisted Titania Tubular Nanoribbons Prepared Through Sol-gel Transcription.

Single-handed twisted titania tubular nanoribbons were prepared through sol-gel transcription using a pair of enantiomers. Handedness was controlled by that of the template. The obtained samples were characterized using field-emission electron microscopy, transmission electron microscopy, diffuse reflectance circular dichroism (DRCD), and X-ray diffraction. The DRCD spectra indicated that the titania nanotubes exhibit optical activity. Although the tubular structure was destroyed after being calcined at 700 °C for 2.0 h, DRCD signals were still identified. However, the DRCD signals disappeared after being calcined at 1000 °C for 2.0 h. The optical activity of titania was proposed to be due to chiral defects. Previous results showed that straight titania tubes could be used as asymmetric autocatalysts, indicating that titania exhibit chirality at the angstrom level. Herein, it was found that they also exhibit DRCD signals, indicating that there are no obvious relationships between morphology at the nano level and chirality at the angstrom level. The nanotube chirality should originate from the chiral defects on the nanotube inner surface. The Fourier transform infrared spectra indicated that the chirality of the titania was transferred from the gelators through the hydrogen bonding between N-H and Ti-OH.

Chirality of the 1,4-phenylene-silica nanoribbons at the nano and angstrom levels.

We reported the preparation of chiral 1,4-phenylene-silicas, using a sol-gel transcription approach, by self-assembly using low-molecular-weight gelators as templates. The silicas exhibited chirality at both the nano and angstrom levels. However, the relation between the chirality at the nano level and that at the angstrom levels has not been well studied. In this study, chiral 1,4-phenylene-silica nanoribbons were prepared by the self-assemblies of three chiral cationic gelators derived from amino acids as templates. These samples were characterized using field-emission scanning electron microscopy, transmission electron microscopy, x-ray diffraction, and circular dichroism. The results indicated that the handedness of the nanoribbons and the stacking of the aromatic rings were controllable. Although the nanoribbons exhibited left-handedness at the nano level, the stacking of the aromatic rings could exhibit left- or right-handedness. The handedness of the nanoribbons at the nano level was controlled by the organic self-assembly of the gelator. However, the stacking of the aromatic rings seemed to be controlled by the gelator itself.

Formation of ethylene-silica nanofibers with concentric circular mesopores inside and lamellar mesopores on the surfaces.

Ethylene-silica nanofibers with concentric circular mesopores inside and lamellar mesopores outside were prepared using stearyltrimethylammonium bromide (STAB) as template and (S)-beta-citronellol as a co-structure-directing agent. They were formed at the (S)-beta-citronellol/STAB molar ratio range of 3:1 to 4:1. Field emission scanning electron microscopy and transmission electron microscopy images taken after different reaction times revealed a phase transition from hexagonal to lamellar phase on the surface of the organic-inorganic hybrid silica nanofibers. The nanofibers with concentric circular pore channels were proposed to be formed from spherical micelles. With increasing the (S)-beta-citronellol/STAB molar ratio from 0.5:1 to 5:1, the morphology changed from short hexagonal rod to long nanofiber, and then to shrunk multilamellar vesicle. Moreover, 1,4-phenylene-silica nanofibers and nanoparticles with concentric circular mesopores inside and lamellar mesopores outside were also prepared.

Let-7b regulates the expression of the growth hormone receptor gene in deletion-type dwarf chickens.

BACKGROUND: A deletion mutation in the growth hormone receptor (GHR) gene results in the inhibition of skeletal muscle growth and fat deposition in dwarf chickens. We used microarray techniques to determine microRNA (miRNA) and mRNA expression profiles of GHR in the skeletal muscles of 14-day-old embryos as well as 7-week-old deletion-type dwarf and normal-type chickens. Our aim was to elucidate the miRNA regulation of GHR expression with respect to growth inhibition and fat deposition. RESULTS: At the same developmental stages, different expression profiles in skeletal muscles of dwarf and normal chickens occurred for four miRNAs (miR-1623, miR-181b, let-7b, and miR-128). At different developmental stages, there was a significant difference in the expression profiles of a greater number of miRNAs. Eleven miRNAs were up-regulated and 18 down-regulated in the 7-week-old dwarf chickens when compared with profiles in 14-day-old embryos. In 7-week-old normal chickens, seven miRNAs were up-regulated and nine down-regulated compared with those in 14-day-old embryos. In skeletal muscles, 22 genes were up-regulated and 33 down-regulated in 14-day-old embryos compared with 7-week-old dwarf chickens. Sixty-five mRNAs were up-regulated and 108 down-regulated in 14-day-old embryos as compared with 7-week-old normal chickens. Thirty-four differentially expressed miRNAs were grouped into 18 categories based on overlapping seed and target sequences. Only let-7b was found to be complementary to its target in the 3' untranslated region of GHR, and was able to inhibit its expression. Kyoto Encyclopedia of Genes and Genomes pathway analysis and quantitative polymerase chain reactions indicated there were three main signaling pathways regulating skeletal muscle growth and fat deposition of chickens. These were influenced by let-7b-regulated GHR. Suppression of the cytokine signaling 3 (SOCS3) gene was found to be involved in the signaling pathway of adipocytokines. CONCLUSIONS: There is a critical miRNA, let-7b, involved in the regulation of GHR. SOCS3 plays a critical role in regulating skeletal muscle growth and fat deposition via let-7b-mediated GHR expression.

Characterization of 4,4'-biphenylene-silicas and a chiral sensor for silicas.

The CD spectra of chiral 4,4'-biphenylene-silicas were measured and simulated using time-dependent density functional theory and a chiral sensor for silicas was developed.

Helical periodic mesoporous 1,4-phenylene-silica nanorods with chiral crystalline walls.

Helical periodic mesoporous 1,4-phenylene-silica nanorods with chiral crystalline walls were prepared using the self-assembly of a pair of enantiomers as templates.

Preparation of mesoporous silica nanoribbons and nanoflakes with short pore channels using a chiral amphiphile.

A chiral cationic low-molecular-weight amphiphile, derived from L-alanine, was synthesized. Templated by the self-assemblies of the amphiphile, sol-gel reactions were carried out to control the morphologies and pore architectures of mesoporous silicas. The results reveal that the morphologies and pore architectures of mesoporous silicas are sensitive to the reaction conditions, such as temperature and the concentration of NaOH. When the reaction was carried out at 25 degrees C, righthanded coiled mesoporous silica nanoribbons with short pore channels were formed, most of which coiled tightly to form nanorods. However, at 80 degrees C, mesoporous silica nanoflakes with vertical pore channels were obtained.

Artificial frustule prepared through a single-templating approach.

An "artificial frustule" was prepared through a single-templating approach, where the self-assembled architecture undergoes a transition from cocoons with pore channels parallel to the surface, to hollow spheres with perpendicular pore channels.

Preparation of helical mesoporous ethylene-silica nanofibers with lamellar mesopores on the surfaces.

Helical ethylene-silica nanofibers with chiral pore channels inside and lamellar pores on the surfaces were prepared using cetyltrimethylammonium bromide and (S)-beta-citronellol as a co-structure-directing agent under basic conditions, the formation mechanism of which was studied by taking field-emission scanning electron microscopy images after different reaction times.

Supramolecular hydrogels inspired by collagen for tissue engineering.

Supramolecular hydrogels are promising biomaterials for cell culture in 2-D and 3-D environments. Inspired by the chemical structure of collagen, which bears the repeating tripeptide of glycine-Xaa-4R-hydroxyproline (GXO; Xaa is any one of the natural amino acids), we designed and synthesized a small library of supramolecular hydrogelators (a total of 6). We found that four of the hydrogels were suitable for NIH 3T3 cell culture in the 2-D environments. Gel 2, the best hydrogel, has properties that are similar to those of collagen for 3T3 cell culture. These findings not only provide more supramolecular hydrogel candidates for tissue engineering, but also offer a new strategy for designing biomaterials that mimic nature.

Control the diameters of mesoporous silica nanotubes by varying stirring time.

A chiral cationic gelator derived from L-alanine was synthesized. Sol-gel transcriptions were carried out to control mesoporous silica nanostructures using the organic self-assemblies of this gelator as templates. It was found that the morphologies of the obtained mesoporous silicas were sensitive to stirring time. With increasing the stirring time, the morphologies of mesoporous silicas changed from nanotubes constructed by double twisted nanoribbons to those constructed by single-strip coiled nanoribbons. The diameters of the nanotubes increased from 80 to 400 nm. This result indicated that the formation of the nanotubes following a dynamic templating process. For a better understanding the pore architectures, the TEM images of the mesoporous silicas were simulated using the 3D studio MAX software.

Formation of hollow mesoporous silica nanoworm with two holes at the terminals.

A chiral low-molecular-weight amphiphile, L- 18Ala11PyPF(6), was synthesized from L-alanine. Hollow silica nanoworms with circular pore channels parallel to the shell surfaces and holes at the terminals were prepared using the self-assemblies of it as templates via a single-templating approach. The formation of this hierarchical structure was studied by taking TEM images after different reaction time and changing reaction conditions. It was found that the morphologies of the amphiphile-silica assemblies changed gradually during the sol-gel transcription process.

Water-soluble phenylpropanoid constituents from aerial roots of Ficus microcarpa.

New water-soluble phenylpropanoid constituents, ficuscarpanoside A, guaiacylglycerol 9-O-beta-D-glucopyranoside, and erythro-guaiacylglycerol 9-O-beta-D-glucopyranoside, along with known guaiacylglycerol, erythro-guaiacylglycerol, 4-methoxy guaiacylglycerol 7-O-beta-D-glucopyranoside, and 3-(4-hydroxy-3-methoxy phenyl) propan-1,2-diol, have been isolated from the aerial roots of Ficus microcarpa. Their structures were elucidated on the basis of 1D and 2D NMR experiments.