Microstructural characteristics of diecast AlMgSiMn alloy

Solidification and microstructural characteristics of Al-5wt.%Mg-1.5wt.%Si-0.6wt.%Mn- 0.2wt.%Ti alloy have been investigated in high pressure die casting. The average size of dendrites and fragmented dendrites of the primary α-Al phase formed in the shot sleeve is 43μm, and the globular α-Al grains formed inside the die cavity is 7.5μm. Solidification inside the die cavity also forms the lamellar Al-Mg2Si eutectic phase and the Fe-rich intermetallics. The size of the eutectic cells is about 10μm, in which the lamellar α-Al phase is 0.41μm thick. The Fe-rich intermetallic compound exhibits a compact morphology and is less than 2μm. Calculations using the Mullins and Sekerka stability criterion reveal that the solidification of the primary α-Al phase inside the die cavity has completed before the spherical α-Al globules begin to lose their stability, but the α-Al grains formed in the shot sleeve exceed the limit of spherical growth and therefore exhibit a dendritic morphology

Creation of partial band gaps in anisotropic photonic-band-gap structures

The photonic-band-gap (PBG) structure composed of an anisotropic-dielectric sphere in uniform dielectric medium is studied by solving Maxwell’s equations using the plane-wave expansion method. In particular, for a uniaxial material with large principal refractive indices and sufficient anisotropy between them, the photonic band structures possess a full band gap in the whole Brillouin zone for a diamond lattice. Furthermore, in the 1/3 partial Brillouin zone where the Bloch wave vector has a dominant component along the extraordinary axis of uniaxial sphere, the photonic band structures are found to exhibit full band gaps for all the other lattices such as face-centered-cubic, body-centered-cubic, and simple-cubic lattices, although a complete band gap does not open in the whole Brillouin zone. The partial band gaps persist at a very low filling fraction of uniaxial sphere. This phenomenon is attributed to the breakdown of the photonic band degeneracy at high-symmetry points of the Brillouin zone by the anisotropy of material dielectricity. The combination of such an anisotropic PBG structure with the self-arrangement technique of colloidal crystal may provide a possible way to fabricate the three-dimensional photonic crystal in visible and infrared regimes. The application of a strong electric field may bring into alignment the extraordinary axis of uniaxial sphere as this configuration of spheres is most favorable thermodynamically.published_or_final_versio

A Novel Biphasic-Current-Pulse Calibration Technique for Electrical Neural Stimulation

One of the major challenge in neural prosthetic device design is to ensure charge-balanced stimulation. This paper presents a new calibration technique to minimize the mismatch between anodic and cathodic current amplitudes. The proposed circuit mainly consists of a digital and an analog calibration, where a successive approximation register (SAR) logic and a comparator are used in digital calibration while a source follower is adopted in analog calibration. With a 0. 18 μm high voltage CMOS process, the simulation shows that the maximum current mismatch is 45 nA (<0.05%).published_or_final_versio

Electrospinning, characterization and in vitro biological evaluation of nanocomposite fibers containing carbonated hydroxyapatite nanoparticles

Poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) fibers containing carbonated hydroxyapatite (CHA) nanoparticles with different CHA amounts (5, 10 and 15 wt%) were electrospun with the aid of ultrasonic power for dispersing the nanoparticles. Scanning electron microscopy and energy-dispersive x-ray spectroscopy results showed that the distribution of CHA within the CHA/PHBV nanocomposite fibers was homogeneous when the CHA content was 10 wt%. Slight particle agglomeration occurred when the CHA content was 15 wt%. The diameters of the electrospun CHA/PHBV nanocomposite fibers and PHBV polymer fibers were around 3 μm. Fourier transform infrared spectroscopic analysis further confirmed the presence of CHA in CHA/PHBV nanocomposite fibers. Both PHBV and CHA/PHBV fibrous membranes exhibited similar tensile properties. Compared with PHBV solvent-cast film, the PHBV fibrous membrane was hydrophobic but the incorporation of CHA nanoparticles dramatically enhanced its wettability. In vitro studies revealed that both types of electrospun fibrous membranes (PHBV and CHA/PHBV) supported the proliferation of human osteoblastic cells (SaOS-2). The alkaline phosphatase activity of SaOS-2 cells seeded on the CHA/PHBV fibrous membranes was higher than that of the cells seeded on the PHBV fibrous membranes after 14 days of cell culture. The electrospun CHA/PHBV nanocomposite fibrous membranes show promises for bone tissue engineering applications. © 2010 IOP Publishing Ltd.postprin

A study of Al1-xInxN growth by reflection high-energy electron diffraction-incorporation of cation atoms during molecular-beam epitaxy

Molecular-beam epitaxy of Al1-x Inx N alloys with different indium (In) contents, x, were studied by in situ reflection high-energy electron diffraction (RHEED). Growth rates of the alloys were measured by the RHEED intensity oscillations for different source flux conditions, while the lattice parameters were derived from the diffraction patterns. It was found that under the excess nitrogen growth regime, incorporation of aluminum was complete whereas incorporation of In atoms was incomplete even at temperatures below 400 °C. © 2008 American Institute of Physics.published_or_final_versio

Comparative study of intestine length, weight and digestibility on different body weight chickens

This experiment was conducted to compare the difference of digestibility on different body weight chickens. Twenty-seven (27) 58-week-old New Yangzhou Chickens of three grade sizes (small 2.0 kg, medium 2.5 kg, and large 3.0 kg) were selected and distributed into three groups (Groups 1 to 3) of nine birds/group, and each group was represented by three replicates. Nutrient retention ratio was determined by adopting whole gather excretion method. In the end of metabolism experiment, all the birds were killed, and the intestine length and intestine weight were measured. Results show that, the amount of feed intake and excretion increased along with body weight gain; the feed intake and excretion in group 3 were significantly higher than that in group 1 (P &lt; 0.05). The sidelong lengths in the three groups were evidently different. Although, the intestinal length as well as the length of the jejunum, ileum and rectum appeared to be gradually improved with the body weight increase, there were no significant differences among the three groups (P &gt; 0.05). The weightier the intestines, the more was body weight of the birds. The retention ratio of energy, crude fiber and neutral detergent fiber increased with body weight gain, but the differences were not significant (P &gt; 0.05). It was concluded that there was no correlation between body weight and digestibility.Keywords: Digestibility, body weight, cock.African Journal of Biotechnology Vol. 12(32), pp. 5097-510

Regenerating plants from in vitro culture of Erigeron breviscapus leaves

A protocol to efficiently achieve plant regeneration from leaf explants of Erigeron breviscapus (Compositae) has been developed. Leaf explants produced calli on Murashige and Skoog&#8217;s (1962) basal medium (MS) supplemented with 6-benzylaminopurine (BAP) (0.4 mM) and 2,4-dichlorophenoxyacetic acid (2,4-D) (0.4-22.6 mM) under a 16-h photoperiod. Direct adventitious shoots were induced from leaf explants on MS medium containing BAP (22.2 mM) and IAA (5.7 mM) under the light treatment. The effect of the dark incubation on shoot regeneration from leaves indicated that 15 days of darkness permitted a higher regeneration frequency (82.6%) on the medium supplemented with BAP (4.4 mM) and indole-3- acetic acid (IAA) (0.6 mM). Regenerated shoots were rooted on MS medium with or without naphthaleneacetic acid (NAA). Plantlets were cultivatable in the greenhouse after acclimatization

Double In Situ Approach for the Preparation of Polymer Nanocomposite with Multi-functionality

A novel one-step synthetic route, the double in situ approach, is used to produce both TiO2nanoparticles and polymer (PET), and simultaneously forming a nanocomposite with multi-functionality. The method uses the release of water during esterification to hydrolyze titanium (IV) butoxide (Ti(OBu)4) forming nano-TiO2in the polymerization vessel. This new approach is of general significance in the preparation of polymer nanocomposites, and will lead to a new route in the synthesis of multi-functional polymer nanocomposites

Macroscopic Klein tunneling in spin-orbit-coupled Bose-Einstein condensates

We propose an experimental scheme to detect macroscopic Klein tunneling with spin-orbit-coupled Bose-Einstein condensates (BECs). We show that a nonlinear Dirac equation with tunable parameters can be realized with such BECs. Through numerical calculations, we demonstrate that macroscopic Klein tunneling can be clearly detected under realistic conditions. Macroscopic quantum coherence in such relativistic tunneling is clarified and a BEC with a negative energy is shown to be able to transmit transparently through a wide Gaussian potential barrier. © 2012 American Physical Society.published_or_final_versio

Current concepts in odontohypophosphatasia form of hypophosphatasia and report of two cases

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