Nanocarrier‐Mediated Codelivery of Small Molecular Drugs and siRNA to Enhance Chondrogenic Differentiation and Suppress Hypertrophy of Human Mesenchymal Stem Cells

Cartilage loss is a leading cause of disability among adults, and effective therapy remains elusive. Human mesenchymal stem cells (hMSCs), which have demonstrated self‐renewal and multipotential differentiation, are a promising cell source for cartilage repair. However, the hypertrophic differentiation of the chondrogenically induced MSCs and resulting tissue calcification hinders the clinical translation of MSCs for cartilage repair. Here, a multifunctional nanocarrier based on quantum dots (QDs) is developed to enhance chondrogenic differentiation and suppress hypertrophy of hMSCs simultaneously. Briefly, the QDs are modified with β‐cyclodextrin (β‐CD) and RGD peptide. The resulting nanocarrier is capable of carrying hydrophobic small molecules such as kartogenin in the hydrophobic pockets of conjugated β‐CD to induce chondrogenic differentiation of hMSCs. Meanwhile, via electrostatic interaction the conjugated RGD peptides bind the cargo siRNA targeting Runx2, which is a key regulator of hMSC hypertrophy. Furthermore, due to the excellent photostability of QDs, hMSCs labeled with the nanocarrier can be tracked for up to 14 d after implantation in nude mice. Overall, this work demonstrates the potential of our nanocarrier for inducing and maintaining the chondrogenic phenotype and tracking hMSCs in vivo.     

Channel management in microcell/macrocell cellular radio systems

In this paper, we study spectrum management in a two-tier microcell/macrocell cellular system. Two issues are studied: micro-macro cell selection and frequency spectrum partitioning between microcells and macrocells. To keep the handoff rate in a two-tier cellular system at an acceptable level, low mobility users (with speed υ0 ) should undergo handoffs at microcell boundaries, and high mobility users (with speed υ>V₀) should undergo handoffs at macrocell boundaries. The mobile determines user mobility from microcell sojourn times and uses it for channel assignment at call origination and handoff. The probability of erroneous assignment of a mobile to a microcell or macrocell is shown to be significantly lower than previous approaches. We investigate the optimal velocity threshold, V₀, and propose that it may be dynamically adjusted according to traffic load. Finally, we propose a systematic way for finding an optimal partition of frequency spectrum between microcells and macrocells. This partitioning is based on the traffic load and velocity distribution of mobiles in the system     

Three-dimensional virtual-reality surgical planning and soft-tissueprediction for orthognathic surgery

Complex maxillofacial malformations continue to present challenges in analysis and correction beyond modern technology. The purpose of this paper is to present a virtual reality workbench for surgeons to perform virtual orthognathic surgical planning and soft-tissue prediction in three dimensions. A resulting surgical planning system, i.e., three-dimensional virtual reality surgical planning and soft-tissue prediction for orthognathic surgery, consists of four major stages: computed tomography (CT) data post-processing and reconstruction, three-dimensional (3-D) color facial soft-tissue model generation, virtual surgical planning and simulation, soft-tissue-change preoperative prediction. The surgical planning and simulation are based on a 3D CT reconstructed bone model, whereas the soft-tissue prediction is based on color texture-mapped and individualized facial soft-tissue model. Our approach is able to provide a quantitative osteotomy-simulated bone model and prediction of postoperative appearance with photorealistic quality. The prediction appearance can be visualized from any arbitrary viewing point using a low-cost personal computer-based system. This cost-effective solution can be easily adopted in any hospital for daily use     

Formation of Gold and Silver Nanoparticle Arrays and Thin Shells on Mesostructured Silica Nanofibers

Mesostructured silica nanofibers synthesized in high yields with cetyltrimethylammonium bromide as the structure‐directing agent in HBr solutions are used as templates for the assembly of Au and Ag nanoparticles and the formation of thin Au shells along the fiber axis. Presynthesized spherical Au and Ag nanoparticles are adsorbed in varying amounts onto the silica nanofibers through bifunctional linking molecules. Nonspherical Au nanoparticles with sharp tips are synthesized on the nanofibers through a seed‐mediated growth approach. The number density of nonspherical Au nanoparticles is controlled by varying the amount of seeded nanofibers relative to the amount of supplied Au precursor. This seed‐mediated growth is further used to form continuous Au shells around the silica nanofibers. Both the Au‐ and Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures and silica/Au core/shell fibers exhibit extinction spectra that are distinct from the spectra of Au and Ag nanoparticles in solution, indicating the presence of new surface plasmon resonance modes in the silica/Au core/shell fibers and surface plasmon coupling between closely spaced metal nanoparticles assembled on silica nanofibers. Spherical Au‐ and Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures are further used as substrates for surface‐enhanced Raman spectroscopy, and the enhancement factors of the Raman signals obtained on the Ag‐nanoparticle/silica‐nanofiber hybrid nanostructures are 2 × 10⁵ for 4‐mercaptobenzoic acid and 4‐mercaptophenol and 7 × 10⁷ for rhodamine B isothiocyanate. These hybrid nanostructures are therefore potentially useful for ultrasensitive chemical and biological sensing by using molecular vibrational signatures.     

传统中药现代化--中药健康食品的开发

传统中药是现代生活健康的宝库,其功效在保健及慢性疾病的治疗方面尤其显著,并已备受世界重视.要成功将中药引进世界市场,最基本要求是要从科学方法去证明其效用及安全性;更重要是依从传统中医学对复方应用的要求去作研究.本文陈述了我们对传统中药古方"生脉散"研究及开发抗氧化健康食品的经验.透过现代生化及药理技术,我们发现"生脉散"中的五味子含丰富的抗氧化活性成分,为传统中医学利用"生脉散"治疗心脏病提供了理论依据.     

Limitation of the Kirchhoff boundary conditions for aerial imagesimulation in 157-nm optical lithography

The aerial images of half-wavelength features with 0° and 180° phases obtained by using the Kirchhoff boundary conditions are compared with those obtained by using rigorous electromagnetic field computation for 248-nm lithography and 157-nm lithography. The discrepancies between the aerial images computed by the two methods are large at both wavelengths, but they are much larger for TM polarization at the wavelength λ=157 nm. These discrepancies are due to diffraction effects in the aperture regions, which are more pronounced at λ=157 nm because of the larger ratio of the thickness of the chromium absorber to the wavelength required at λ=157 nm for a given attenuation factor. This shows that diffraction effects in the aperture regions must be included when simulating aerial images in 157-nm lithography     

Utilities and two-way customer communication systems

The concept of providing energy conservation programs with monitoring and control via two-way communication (TWCC) systems will be one of the solutions that utilities will employ in the conservation of the nation's valuable natural resources. The development of microelectronic technology is changing the manner in which meters will be read. There are many methods currently available in the market that enable retrieval of data remotely from a customer's premise. The potential of this technology and its applications can be endless. In the area of automatic meter reading (AMR), current technology is in a state of evolution where no single method excels. Development of the new “information superhighway” industry is likely to promote standards based upon open systems and open protocols. Current AMR technologies are described     

Development of Metallic Hermetic Sealing for MEMS Packaging for Harsh Environment Applications

Hermetic sealing of microelectromechanical system sensors is indispensable to ensure their reliable operation and also to provide protection during fabrication. This work proposes two prospective candidates for hermetic sealing for rugged environment applications, i.e., Al-Ge and Pt-In. Al-Ge was chosen due to its compatibility with complementary metal–oxide–semiconductor technology. Pt-In possesses the highest remelting temperature among all the solder systems, which is desired for high-temperature applications in both the energy and aerospace industries. The various bonding parameters for Al-Ge eutectic bonding and Pt-In transient liquid-phase (TLP) bonding have been optimized, and their influence on the bond quality is reported. Optimization of bonding parameters has been carried out with the objective of ensuring void-free bonds. A new configuration for stacking Al-Ge thin films has been demonstrated to tackle the issue of loss of Ge prior to bonding, since native Ge oxides are soluble in deionized water. The impact of solid-state aging prior to Al-Ge eutectic bonding has been investigated. The method of tailoring the phases in the Pt-In joint is also discussed. The prospects and constraints of eutectic and TLP bonding from the hermeticity perspective are discussed in detail. Furthermore, changes in the microstructure under aging at 300°C up to 500 h and the resulting influence on the mechanical properties are presented. The overall finding of this work is that Al-Ge can achieve better mechanical and hermetic performance for high-temperature applications.     

Reliability of Au-Ge and Au-Si Eutectic Solder Alloys for High-Temperature Electronics

High-temperature electronics will facilitate deeper drilling, accessing harder-to-reach fossil fuels in oil and gas industry. A key requirement is reliability under harsh conditions for a minimum continuous operating time of 500?h at 300°C. Eutectic solder alloys are generally favored due to their excellent fatigue resistance. Performance of Au-Ge and Au-Si eutectic solder alloys at 300°C up to 500?h has been evaluated. Nanoindentation results confirm the loss of strength of Au-Ge and Au-Si eutectic solder alloys during thermal aging at 300°C, as a result of grain coarsening. However, the pace at which the Au-Ge eutectic alloy loses its strength is much slower when compared with Au-Si eutectic alloy. The interfacial reactions between these eutectic solder alloys and the underbump metallization (UBM), i.e., electroless nickel immersion gold (ENIG) UBM and Cu/Au UBM, have been extensively studied. Spalling of Au₃Cu intermetallic compound is observed at the interface between Au-Ge eutectic solder and the Cu/Au UBM, when aged at 300°C for 500?h, while the consumption of ENIG UBM is nominal. Unlike the Au-Si solder joint, hot ball shear testing at high temperature confirmed that the Au-Ge joint on ENIG UBM, when aged at 300°C for 500?h, could still comply with the minimum qualifying bump shear strength based on the UBM dimension used in this work. Thus, it has been determined that, among these two binary eutectic alloys, Au-Ge eutectic alloy could fulfill the minimum requirement specified by the oil and gas exploration industry.