Application of an X-ray microscopy technique to evaluate tissue-engineered bone-scaffold constructs

Elemental composition and structural analysis are important considerations in evaluating osseous matrix formation in tissue-engineered bone constructs. Using X-ray spectroscopy techniques, such as the X-ray scanning analytical microscope (XSAM), enables the mapping of elements with simultaneous structural imaging. The aim of this study was to evaluate the feasibility of this microscopy technique to analyze tissue-engineered samples. Fused deposition modeling (FDM), a rapid prototyping technology, was used to fabricate 3-D scaffolds made of polycaprolactone (PCL)–hydroxylapatite (HA) (90/10 wt.%). The scaffolds had a regular architecture and the honeycomb-like pores were fully interconnected with a total matrix porosity of 70%. Biopsies of human calvarial corticocancellous bone were harvested and a primary explant system of the morcellized grafts was established within the PCL–HA constructs.

Tissue constructs were cultured in vitro for 3 weeks and then implanted into the back of Balb C nude mice. Grafts were explanted after 17 weeks and tissue formation was assessed via XSAM and CT scan and histology.

Outgrowth from osteoblasts from the bone chips started after 2 weeks in culture, with cells migrating radially into the composite constructs. Osteocalcin levels showed an increasing tendency during the 3-week culture period. After 17 weeks in vivo, areas of ectopic bone formation could be detected throughout the whole construct, compared to the control implants where only fibrous tissue formation was present. In the XSAM, calcium- and phosphorus-enriched bands presented a relatively even distribution with some dense spots. Quantitative elemental analysis revealed an average X-ray intensity of 131 cps for calcium in a mapped area of 2 mm². Trichrome Goldner staining showed good vascularization as well as irregular osteoid formation and mineralization of the newly formed woven bone-like tissue.

In this study, we were able to show that the XSAM is a useful analytical technique which enabled us to trace elements simultaneously and provides structural image with mapping information in tissue-engineered samples.     

The Third-Party Logistics Services and Globalization of Manufacturing

Cross-border production chains of manufacturing require coordination and logistics. Third-party logistics services have thus taken this role as a link in the globalization of economic activities. Distriparks, a provider of total logistics to manufacturing, have emerged in Singapore to offer customized distribution and inventory management. Established as a traditional entrepôt by international trading, the city-state has revamped its distribution industry when transnational corporations come to choose Singapore as regional centre and local firms venture into the region. Distribution has regained its vitality in the global economy. It is demonstrated that distriparks have facilitated the restructuring of Singapore manufacturing and altered the internal structure of firms in their space utilization. Thereafter, a changing profile of industrial landscape, high-density industrial land use, and industrial agglomeration ensues.     

Ultra-thin decoupled plasma nitridation (DPN) oxynitride gate dielectric for 80-nm advanced technology

Balancing gate leakage reduction, device performance, and gate dielectric reliability is a major challenge for oxynitride used as a gate dielectric for advanced technology. As compared to RTONO oxynitride, pMOSFET threshold voltage shift and transconductance degradation have been problematic for devices using remote plasma nitridation (RPN) or decoupled plasma nitridation (DPN) process due to non-optimal nitrogen profile in the film. In this paper, we report that the nitrogen profile of DPN gate dielectric can be engineered primarily by tuning the plasma pressure after optimizing other DPN process parameters to solve these problems. An EOT of 15 /spl Aring/ (23-/spl Aring/ NMOS CETinv) DPN oxynitride is demonstrated to have an acceptable pMOS Vt, comparable transconductance, significantly (/spl sim/30/spl times/) longer pMOS time-to-breakdown reliability for packaged devices, and 5/spl times/ gate leakage reduction relative to a high quality RTONO used in industry. The high quality ultrathin DPN film is fabricated in a commercially available system, which is compatible with standard CMOS processing technology. These encouraging results make high-pressure DPN oxynitride an attractive gate dielectric candidate for 80-nm advanced technology and beyond.     

Synthesis and Electronic Spectra of Some Monoazo Disperse Dyes Derived from N-Methylindoline

Several monoazo dyes suitable for transfer printing have been prepared from N-methylindoline and compared with the corresponding derivatives of N-methyl -12,3,4-tetrahy-droquinoline (kairoline). The presence of a five-membered terminal ring system leads to diminished π-interaction and results in modest hypsochromic and hypochromic shifts of the visible absorption band, relative to the analogous kairo-line derivatives, together with some deterioration in light-fastness properties on synthetic-polymer fibres.     

ZnSe nanotrenches: formation mechanism and its role as a 1D template

High-resolution transmission electron microscopy was used to characterize the microstructures of ZnSe nanotrenches induced by mobile Au-alloy droplets. The contact side interfaces between the AuZn_δ alloy droplets and the ZnSe as well as the four side walls of the resulting <011>-oriented nanotrenches were found all belong to the {111} plane family, with the front and back walls being the {111}A planes while the other two side walls being the {111}B planes. These findings offer a deeper understanding on the formation mechanism of the nanotrenches. Pure Au nanodashes were formed upon further deposition of Au on the nanotrenches.     

A review on the current research trends in ductile regime machining

Ductile regime machining is an alternative method for polishing of brittle materials to obtain a high quality surface finish by a ductile or plastic material removal process. Hence, there is a growing interest to study ductile regime machining over several decades. This paper reviews current state of research and development in ductile regime machining. The research and development associated with mechanism of brittle–ductile transition, surface integrity, and the factors influencing ductile regime machining are discussed in details in this paper.     

Electromechanical design and construction of a rotating radio-frequency coil system for applications in magnetic resonance

While recent studies have shown that rotating a single radio-frequency (RF) coil during the acquisition of magnetic resonance (MR) images provides a number of hardware advantages (i.e., requires only one RF channel, avoids coil-coil coupling and facilitates large-scale multinuclear imaging), they did not describe in detail how to build a rotating RF coil system. This paper presents detailed engineering information on the electromechanical design and construction of a MR-compatible RRFC system for human head imaging at 2 T. A custom-made (bladeless) pneumatic Tesla turbine was used to rotate the RF coil at a constant velocity, while an infrared optical encoder measured the selected frequency of rotation. Once the rotating structure was mechanically balanced and the compressed air supply suitably regulated, the maximum frequency of rotation measured ~14.5 Hz with a 2.4% frequency variation over time. MR images of a water phantom and human head were obtained using the rotating RF head coil system.     

Experimental characterization and modelling of electromigration lifetime under unipolar pulsed current stress

The electromigration behaviour of Cu/SiCOH interconnects carrying unipolar pulsed current with long periods (i.e. 2, 16, 32 and 48 h) is presented in this study. Experimental observations suggest that the electromigration behaviour during void growth can be described by the ON-time model and that the lifetime of the Cu/SiCOH interconnects is inversely related to the duty cycle. Numerical simulation is carried out to compute the time required to nucleate a void under unipolar pulsed current stress conditions. The time to void nucleation is found to vary proportionally to the inverse square of the duty cycle and is independent of frequency at 1 Hz and higher. By computing the stress evolution in interconnects with short length, it was shown that the product of the unipolar pulsed current’s duty cycle and current density, i.e. average current density, is equivalent to the current density of a constant current (D.C.) stress. The simulation results suggest (d · jL)_crit as the equivalent critical current density-length product under unipolar pulsed current condition. Both the experimental and simulation results show that duty cycle has an effect on the electromigration lifetime of interconnects carrying unipolar pulsed current.     

嵌入式存储器测试

随着存储器需求的增加以及制造技术的进步,嵌入式存储器在SOC系统中的地位越来越重要。与传统的分立存储器件测试相比,嵌入式存储器的测试呈现出新的挑战。本文试图全面叙述嵌入式存储器的各种结构,并介绍各种DFT（可测性设计）测试技术,如SCAN〔扫描〕、MBIST（存储器内建自测试）以及BISR（内建自修复）。     

Adaptive tuning piecewise cubic Hermite interpolation with Wiener filter in wavelet domain for scanning electron microscope images

Image processing is introduced to remove or reduce the noise and unwanted signal that deteriorate the quality of an image. Here, a single level two‐dimensional wavelet transform is applied to the image in order to obtain the wavelet transform sub‐band signal of an image. An estimation technique to predict the noise variance in an image is proposed, which is then fed into a Wiener filter to filter away the noise from the sub‐band of the image. The proposed filter is called adaptive tuning piecewise cubic Hermite interpolation with Wiener filter in the wavelet domain. The performance of this filter is compared with four existing filters: median filter, Gaussian smoothing filter, two level wavelet transform with Wiener filter and adaptive noise Wiener filter. Based on the results, the adaptive tuning piecewise cubic Hermite interpolation with Wiener filter in wavelet domain has better performance than the other four methods.