Electrolytic deposition of hydroxyapatite coating on thermal treated Ti-40Zr

In this study, hydroxyapatite (HA) was coated on both thermal treated and untreated Ti-40Zr substrates by means of electrolytic deposition. It was predicted that the HA layer would increase the bioactivity and osteoconductivity of the Ti-40Zr substrate, and a thermal treatment would improve the bonding strength between the HA layer and Ti-40Zr substrate, and prevent the corrosion of the Ti-40Zr substrate. First, the Ti-40Zr samples were annealed at various temperatures (200, 300, 400, 500 and 600°C respectively). After annealing, samples were immersed in a Ca(NO₃)₂ · 4H₂O and (NH₄)₃PO₄ · 3H₂O solution for the electrolytic deposition of the HA coating. Various analyses of the coating were conducted, including surface morphology, phase structure, corrosion resistance, biocompatibility, and bond strength between HA and Ti-40Zr. Experimental results indicated that the bonding strength of the HA coating on the thermal treated Ti-40Zr was markedly improved when compared to that of the HA coating on an untreated Ti-40Zr alloy. The corrosion resistance of Ti-40Zr was also improved by the use of the thermal treatment, as shown by a potentiodynamic polarization test. Finally, osteoblast-like cells cultured on the HA coating surface were found to have proliferated on all samples.     

Toxicity assessment upon augmented biostimulation source to indigenous rhizobium Cupriavidus taiwanensis

This novel-attempt study used chemostat pulse technique (CPT) and transient dynamics of dissolved oxygen (DO) in CSTR to quantify stimulating or inhibitory effects of augmented nutrient sources in the presence of phenol upon Cupriavidus taiwanensis R186. With injected augmented nutrients, phenol degradation performance of R186 was directly dependent on combined toxicity between phenol and the augmented substrate and the biodegradability of phenol. The findings indicated that although phenol was toxic to R186, all augmented nutrient sources still exhibited stimulating effects to bacterial growth of R186 in the presence of phenol. The simulating rankings of augmented nutrients were (1) at 200 mg/L, acetic acid>gluconic acid>yeast extract>glycerol>phenol alone, (2) at 1000 mg/L, gluconic acid>acetic acid>glycerol>yeast extract>phenol alone. This stimulating effect clearly suggested that this combined toxicity was antagonistic. It was also revealed that transient responses of DO seemed to be in parallel with the findings from CPT. It was thus concluded that substrate consumption patterns would play the most significant role in biostimulation to cultures with dual energy sources. This study can help uncover the mysteries of optimal biostimulation for phenol degradation as proposed in previous studies. In addition, this study directly provided a kinetic model to quantify the relative stimulation ranking of augmented nutrients in the presence of phenol for practical bioremediation.     

The Influence of Structural Defect on Mechanical Properties and Fracture Behaviors of Carbon Nanotubes

Due to the limitation of fabrication technologies nowadays, structural or atomistic defects are often perceived in carbon nanotubes (CNTs) during the manufacturing process. The main goal of the study aims at providing a systematic investigation of the effects of atomistic defects on the nanomechanical properties and fracture behaviors of single-walled CNTs (SWCNTs) using molecular dynamics (MD) simulation. Furthermore, the correlation between local stress distribution and fracture evolution is studied. Key parameters and factors under investigation include the number, type (namely the vacancy and Stone-Wales defects), location and distribution of defects. Results show that the nanomechanical properties of the CNTs, such as the elastic modulus, ultimate strength and ultimate strain, are greatly affected by the defects and also their percentage and type. It is also found that the CNTs present a brittle fracture as the strain attains a critical value, and in addition, the fracture crack tends to propagate along the high tensile stress concentration area. Moreover, the distribution pattern of defects is another driving factor affecting the nanomechanical properties of the CNTs and the associated fracture evolutions.     

Cytotoxicity and Immunological Response of Gold and Silver Nanoparticles of Different Sizes

The immunological response of macrophages to physically produced pure Au and Ag nanoparticles (NPs) (in three different sizes) is investigated in vitro. The treatment of either type of NP at ≥10 ppm dramatically decreases the population and increases the size of the macrophages. Both NPs enter the cells but only AuNPs (especially those with smaller diamter) up‐regulate the expressions of proinflammatory genes interlukin‐1 (IL‐1), interlukin‐6 (IL‐6), and tumor necrosis factor (TNF‐α). Transmission electron microscopy images show that AuNPs and AgNPs are both trapped in vesicles in the cytoplasma, but only AuNPs are organized into a circular pattern. It is speculated that part of the negatively charged AuNPs might adsorb serum protein and enter cells via the more complicated endocytotic pathway, which results in higher cytotoxicity and immunological response of AuNPs as compared to AgNPS.     

Simple monopoly price theory in a spatial market

One of main conclusions drawn by prior studies is that in a spatial market, the shape of the demand function can fully determine whether one simple pricing policy is superior to another either on the basis of the firm’s preference or social desirability while there is one assumption that is generally stipulated, namely, that the fixed market area assumption under which the market area is exogenously determined and remains the same under alternative pricing policies. In order to fully understand the impact of a demand function, this paper attempts to reexamine the relative economic advantages between two simple spatial pricing policies in a world with variable market area, that is, the market area is endogenously determined the price charged. We show that the fixed market area assumption is valid only where demand is linear, but no longer holds where demand is nonlinear. Moreover, and more importantly, we show that in a world with variable market area, some conclusions drawn by prior studies on the relative economic benefits of two pricing policies cannot remain valid. The main conclusion of this paper is that even the relative economic benefits of two simple spatial pricing policies is concerned, the impact of economic space is significant.

Effect of Hydrostatic Pressure on Aggregation and Viscoelastic Properties of Tilapia (Orechromis niloticus) Myosin

ABSTRACT: Hydrostatic pressures from 500 to 2000 atmospheres (atm) were applied at 0°C to determine the aggregation and viscoelastic properties of tilapia ( Orechromis niloticus ) myosin. Native myosins were present as long, linear, and single filaments. After a 500-atm treatment, these filaments unfolded and their volume decreased. Upon 1000-atm and 1500-atm treatments, myosins aggregated and formed inseparable network structures. Further, they transformed from viscous sol to elastic gels with a pressure of 500 to 1000 atm. At 2000 atm, the myosin formed irregular aggregates. This study reveals that at 500 atm, myosins unfolded; at 1000 atm, they aggregated, and beyond 1500 atm, they formed both a precipitate and gel.     

Comprehensive study on a novel bidirectional tunnelingprogram/erase NOR-type (BiNOR) 3-D flash memory cell

In this paper a recently proposed bidirectional tunneling program/erase (P/E) NOR-type (BiNOR) flash memory is extensively investigated. With the designated localized p-well structure, uniform Fowler-Nordheim (FN) tunneling is first fulfilled for both program and erase operations in NOR-type array architecture to facilitate low power applications. The BiNOR flash memory guarantees excellent tunnel oxide reliability and is provided with fast random access capability. Furthermore, a three-dimensional (3D) current path in addition to the conventional two-dimensional (2D) conduction is proven to improve the read performance. The BiNOR flash memory is thus promising for low-power, high-speed, and high-reliability nonvolatile memory applications     

Performance evaluation of random power capture on mobile communications

Power assignment schemes are man‐made methods to enhance the capture effect of radio communications. In a previous study, Wen and Yang investigated the combined capture effect of the fixed power assignment scheme, Rayleigh fading, and near–far effect on the performance of packet radios. The performance analysis was limited to an infinite population environment. This assumption is reasonable for a conventional packet radio system with a vast service area. However, for a cellular mobile system, a finite population model should be used. In this paper, we analyse the combined natural and man‐made capture effect on the performance of a cellular system with finite population in each cell. A random power assignment scheme is adopted to produce the man‐made capture. The system throughput and delay are carried out by a Markov model. Some numerical calculations are used to demonstrate the degree of performance improvement. Copyright © 2001 John Wiley & Sons, Ltd.     

Structural design of current-mode biquad filters

This work describes how to generate and design a novel current-mode biquad filter model using tunable multiple-output operational transconductance amplifiers and grounded capacitors (MO-OTA-Cs) for synthesizing both transmission poles and zeros. Transfer functions of low-pass, band-pass, high-pass, notch and all-pass are realized based on the filter model. The theory focuses mainly on establishing a relationship between the cascaded MO-OTA-Cs and the multiple-loop feedback matrix, which makes the structural generation and design formulas. All the filter architectures contain only grounded capacitors, which can absorb parasitic capacitances and require smaller chip areas than floating ones. The simulation results are also presented to confirm the theoretical analysis.