Designing of precomputational-based low-power Viterbi decoder

This work addresses the low-power VLSI implementation of the Viterbi decoder (VD). A new precomputational scheme applied to the trellis butterflies calculation is presented. The proposed scheme is implemented in a 16-state, rate 1/3 VD. Gate-level power verification indicates that the proposed design reduces the power dissipated by the original trellis butterflies calculation by 42%.published_or_final_versio

Interfacial microstructures in ramp type multilayer Josephson junctions studied by TEM

The microstructures of high Tc ramp type Josephson junctions were studied by using transmission electron microscopy. The work was emphasized at the interfacial defects and the influence of the ramp slope. The results show that for the ramp slope angles of 15°~40°, the epitaxy was still remained through all layers at the ramp region without the formation of big grain boundaries. No amorphous layers and secondary phases were observed at the barrier interfaces. For a gentle ramp junction, small misoriented grains appeared in some portions of the barrier. The substrate ramp formed during the ion etching process had little influence on the growth of the upper layers. In junctions with a steep ramp, defects increased near the interface, although the epitaxy of the barrier was of good quality. The results demonstrate that the slope angle of the junction ramp is an important factor that influences the performance of the Josephson junctions.published_or_final_versio

Differentiation of Human Embryonic Stem Cells into Cells with Corneal Keratocyte Phenotype

Corneal transparency depends on a unique extracellular matrix secreted by stromal keratocytes, mesenchymal cells of neural crest lineage. Derivation of keratocytes from human embryonic stem (hES) cells could elucidate the keratocyte developmental pathway and open a potential for cell-based therapy for corneal blindness. This study seeks to identify conditions inducing differentiation of pluripotent hES cells to the keratocyte lineage. Neural differentiation of hES cell line WA01(H1) was induced by co-culture with mouse PA6 fibroblasts. After 6 days of co-culture, hES cells expressing cell-surface NGFR protein (CD271, p75NTR) were isolated by immunoaffinity adsorption, and cultured as a monolayer for one week. Keratocyte phenotype was induced by substratum-independent pellet culture in serum-free medium containing ascorbate. Gene expression, examined by quantitative RT-PCR, found hES cells co-cultured with PA6 cells for 6 days to upregulate expression of neural crest genes including NGFR, SNAI1, NTRK3, SOX9, and MSX1. Isolated NGFR-expressing cells were free of PA6 feeder cells. After expansion as a monolayer, mRNAs typifying adult stromal stem cells were detected, including BMI1, KIT, NES, NOTCH1, and SIX2. When these cells were cultured as substratum-free pellets keratocyte markers AQP1, B3GNT7, PTDGS, and ALDH3A1 were upregulated. mRNA for keratocan (KERA), a cornea-specific proteoglycan, was upregulated more than 10,000 fold. Culture medium from pellets contained high molecular weight keratocan modified with keratan sulfate, a unique molecular component of corneal stroma. These results show hES cells can be induced to differentiate into keratocytes in vitro. Pluripotent stem cells, therefore, may provide a renewable source of material for development of treatment of corneal stromal opacities. © 2013 Chan et al

A totally Self-Checking Dynamic Asynchronous Datapath

This paper investigates the inherent totally self-checking (TSC) property of one type of dynamic asynchronous datapath based on Differential Cascode Voltage Logic (DCVSL). As a result, a totally self-checking dynamic asynchronous datapath architecture is proposed. It is simpler than other similar approaches and represents a new approach to fault tolerant design.published_or_final_versio

Stable controller design for linear systems

This paper is concerned with the problem of suboptimal stable mixed H2/H∞ control for linear time-invariant systems. The designed controllers are required to satisfy a prescribed H∞ performance bound or a prescribed degree of stability. By reducing the stable controller synthesis problem to a multiobjective state feedback control problem for two different state models, sufficient conditions for the solvability of the considered problem are given in terms of solutions to algebraic Riccati equations and matrix inequalities. LMI-based iterative algorithms are developed to solve the stable controller synthesis problem. All of the proposed algorithms are shown to be convergent. An example is given to illustrate the proposed methods.published_or_final_versio

Hands-on reconfigurable robotic surgical instrument holder arm

Abstract: The use of conventional surgical tool holders requires an assistant during positioning and adjustment due to the lack of weight compensation. In this paper, we introduce a robotic arm system with hands-on control approach. The robot incorporates a force sensor at the end effector which realises tool weight compensation as well as hands-on manipulation. On the operating table, the required workspace can be tight due to a number of instruments required. There are situations where the surgical tool is at the desired location but the holder arm pose is not ideal due to space constraints or obstacles. Although the arm is a non-redundant robot because of the limited degrees of freedom, the pseudo-null-space inverse kinematics can be used to constrain a particular joint of the robot to a specific angle while the other joints compensate in order to minimise the tool movement. This allows operator to adjust the arm configuration conveniently together with the weight compensation. Experimental results demonstrated that our robotic arm can maintain the tool position during reconfiguration significantly more stably than a conventional one

Biodegradable cationic poly(carbonates): effect of varying side chain hydrophobicity on key aspects of gene transfection

The degree of hydrophobicity in cationic polymers plays an important but often underappreciated role in the safety and efficacy of gene delivery processes. In order to further elucidate structure-activity relationships of biodegradable cationic poly(carbonate) gene carriers, we synthesized a series of narrowly dispersed homo-polymers via metal-free organocatalytic living ring-opening polymerization (ROP) of cyclic carbonate monomers bearing either alkyl (propyl, hexyl or nonyl) or 4-methyl benzyl halide side chains. The polymers were then quaternized using bis-tertiary amines to install both quaternary ammoniums and tertiary amines for DNA binding and endosomal escape, respectively. Among the polymers with similar molecular lengths and charge densities, it was found that an increase in side chain alkyl spacer length from 3 to 6 carbons significantly enhanced cellular uptake and luciferase gene expression in HepG2 and HeLa cell lines without causing overt hemolysis and cytotoxicity. A further increase of side chain alkyl length to 9 carbons, however, led to a drastic decline in gene expression due to increased cellular toxicity, which was correlated with an increased disruption and lysis of red blood cell membranes. Interestingly, the incorporation of an aromatic 4-methyl benzyl spacer increased DNA binding strength, reduced particle sizes of resultant DNA complexes, and enhanced cellular uptake, leading to improved luciferase gene expression, albeit with higher levels of hemolysis and cytotoxicity. Taken together, the findings of this study demonstrate that a delicate balance between cationic charge density and hydrophobicity could be achieved by utilizing a hexyl spacer in the side chains of cationic poly(carbonates), hence providing insights on the future development of non-viral cationic polymeric gene delivery systems. Statement of Significance: Owing to their ease of synthesis and well-controlled polymerization, biodegradable cationic poly(carbonates) have emerged as a highly promising class of biomaterials for gene delivery. The hydrophobicity of side chains in cationic polymers plays an important but often underappreciated role in influencing key aspects of gene transfection. In our efforts to improve gene transfection and understand structure-activity relationships, we synthesized a series of cationic polymers bearing a common poly(carbonate) backbone, and with side chains containing various hydrophobic spacers (propyl, hexyl, 4-methyl benzyl or nonyl) before the cationic moiety. A moderate degree of hydrophobicity was optimal as the cationic poly(carbonate) with hexyl side chains mediated high gene transfection efficiencies while causing low cytotoxicities. (111 words

Quick and sensitive determination of gene expression of fatty acid synthase in vitro by using real-time polymerase chain reaction amplification (PCR)

Obesity results from an imbalance between energy intake and energy expenditure, which leads to a pathological accumulation of adipose tissue, but the underlying mechanism at gene level, is far from being elucidated. The objective of this study was to investigate the correlation between mRNA express from fatty acid synthase (FAS) with a different glucose level in primary adipocytes by real-time polymerase chain reaction amplification (PCR), which can aid in the understanding of the mechanism of obesity in vitro. By using the following formula, this study was able to quantify the mRNA expression of FAS of unknown samples: Y = -3.156X + 41.21 (Y = threshold cycle, X = log starting quantity). The high concentrations of glucose group significantly improved the mRNA expression of FAS (P < 0.01) rather than 0.25 and 0% concentrations of glucose. These results provide significant data that confirm an association between different glucose level and FAS expression in preadipocytes. The glucose concentration of the high group substantially augmented the mRNA expression of FAS.Key words: Expression, fatty acid synthase, lipid deposition, real-time polymerase chain reaction amplification (PCR)

Inverse-designed diamond photonics

Diamond hosts optically active color centers with great promise in quantum computation, networking, and sensing. Realization of such applications is contingent upon the integration of color centers into photonic circuits. However, current diamond quantum optics experiments are restricted to single devices and few quantum emitters because fabrication constraints limit device functionalities, thus precluding color center integrated photonic circuits. In this work, we utilize inverse design methods to overcome constraints of cutting-edge diamond nanofabrication methods and fabricate compact and robust diamond devices with unique specifications. Our design method leverages advanced optimization techniques to search the full parameter space for fabricable device designs. We experimentally demonstrate inverse-designed photonic free-space interfaces as well as their scalable integration with two vastly different devices: classical photonic crystal cavities and inverse-designed waveguide-splitters. The multi-device integration capability and performance of our inverse-designed diamond platform represents a critical advancement toward integrated diamond quantum optical circuits