The rapid formation of a large rotating disk galaxy three billion years after the Big Bang.

Observations and theoretical simulations have established a framework for galaxy formation and evolution in the young Universe. Galaxies formed as baryonic gas cooled at the centres of collapsing dark-matter haloes; mergers of haloes and galaxies then led to the hierarchical build-up of galaxy mass. It remains unclear, however, over what timescales galaxies were assembled and when and how bulges and disks--the primary components of present-day galaxies--were formed. It is also puzzling that the most massive galaxies were more abundant and were forming stars more rapidly at early epochs than expected from models. Here we report high-angular-resolution observations of a representative luminous star-forming galaxy when the Universe was only 20% of its current age. A large and massive rotating protodisk is channelling gas towards a growing central stellar bulge hosting an accreting massive black hole. The high surface densities of gas, the high rate of star formation and the moderately young stellar ages suggest rapid assembly, fragmentation and conversion to stars of an initially very gas-rich protodisk, with no obvious evidence for a major merger.

Effect of electrochemically deposited apatite coating on bonding of bone to the HA-G-Ti composite and titanium.

The surfaces of hydroxyapatite-glass-titanium (HA-G-Ti) functionally gradient composite and titanium bars were treated with electrochemical apatite deposition, and a cathodic current was applied at 62 degrees C in a solution containing calcium and phosphate ions. Specimens with and without the electrochemical surface treatment were implanted in the femurs of Japanese white rabbits. The rabbits were sacrificed at 3, 6, and 9 weeks after implantation, and the bonding strengths of bone to these specimens were determined by a pull-out method. At 3 and 6 weeks after implantation the specimens with the electrochemical surface treatment showed larger values for the Weibull modulus and characteristic strengths than those of untreated specimens, whereas there was no remarkable difference in the results at 9 weeks. Especially the pull-out strengths of surface-treated specimens were significantly larger than the untreated ones at 3 weeks after implantation. Scanning electron microscopy and Fourier transform infrared absorption spectroscopy of the specimen surface after implantation demonstrated that formation of new bone was enhanced by the electrochemical surface treatment. It can be concluded that the electrochemical surface treatment undoubtedly contributes to the early stage fixation between bone and implant.

Crystal phase of fibrous calcium phosphates prepared with sodium alginate.

This study investigated the effects of preparation conditions on the crystal phase of the fired fiber prepared with sodium alginate. Hydroxyapatite, Ca10(PO4)6(OH)2, hereafter referred to as HA, was only formed in fiber fired at 900 degrees C under proper conditions. There was no significant difference in the crystal phase of the fired fibers prepared using different sodium alginate concentrations and syringe nozzle diameter, although fiber diameters were enlarged with increasing in either. No effects of phosphate type on the crystal phase of the fired fiber were found, but the aging time and the rinsing time had great effects. Sodium calcium phosphate, NaCaPO4, and HA were formed when the aging time was shorter than 5 min. Chlorapatite, Ca5Cl(PO4)3, and HA were formed when the rinsing time was shorter than 3 sec, and HA was formed when the rinsing time was 5 min to 1 hour, beta-TCP, beta-Ca3 (PO4)2, and HA were formed when the rinsing time exceeded 2 weeks.

Factors affecting the transformation of octacalcium phosphate to apatite in vitro.

A fresh octacalcium phosphate (OCP) precipitate without drying and three kinds of dried OCP powders were soaked for 3 weeks in 11 kinds of physiological solutions consisting of different combinations of Ca2+, Mg2+, K+, Na+, HCO3-, HPO4(2-), F-, albumin, collagen and alkaline phosphatase, in three different pH values and at three different temperatures. X-ray diffraction study showed that most of the OCP had been transformed to apatite with low crystallinity after soaking in the solutions without Mg2+. The IR absorption spectra revealed that CO3 was incorporated in the apatite formed from OCP in the solution without Mg2+, whereas OCP changed little after soaking in the solution containing Mg2+. These results suggest that the presence of Mg2+ in the solution is one of the most effective means of inhibiting the transformation of OCP to apatite by interrupting the precipitation process of apatite.