Ferroelectric-carbon nanotube memory devices

One-dimensional ferroelectric nanostructures, carbon nanotubes (CNT) and CNT-inorganic oxides have recently been studied due to their potential applications for microelectronics. Here, we report coating of a registered array of aligned multi-wall carbon nanotubes (MWCNT) grown on silicon substrates by functional ferroelectric Pb(Zr,Ti)O3 (PZT) which produces structures suitable for commercial prototype memories. Microstructural analysis reveals the crystalline nature of PZT with small nanocrystals aligned in different directions. First-order Raman modes of MWCNT and PZT/MWCNT/n-Si show the high structural quality of CNT before and after PZT deposition at elevated temperature. PZT exists mostly in the monoclinic Cc/Cm phase, which is the origin of the high piezoelectric response in the system. Low-loss square piezoelectric hysteresis obtained for the 3D bottom-up structure confirms the switchability of the device. Current-voltage mapping of the device by conducting atomic force microscopy (c-AFM) indicates very low transient current. Fabrication and functional properties of these hybrid ferroelectric-carbon nanotubes is the first step towards miniaturization for future nanotechnology sensors, actuators, transducers and memory devices.     

Integer Linear Programming-Based Bit-Level Optimization for High-Speed FIR Decimation Filter Architectures

Analog-to-digital converters based on sigma-delta modulation have shown promising performance, with steadily increasing bandwidth. However, associated with the increasing bandwidth is an increasing modulator sampling rate, which becomes costly to decimate in the digital domain. Several architectures exist for the digital decimation filter, and among the more common and efficient are polyphase decomposed finite-length impulse response (FIR) filter structures. In this paper, we consider such filters implemented with partial product generation for the multiplications, and carry-save adders to merge the partial products. The focus is on the efficient pipelined reduction of the partial products, which is done using a bit-level optimization algorithm for the tree design. However, the method is not limited only to filter design, but may also be used in other applications where high-speed reduction of partial products is required. The presentation of the reduction method is carried out through a comparison between the main architectural choices for FIR filters: the direct-form and transposed direct-form structures. For the direct-form structure, usage of symmetry adders for linear-phase filters is investigated, and a new scheme utilizing partial symmetry adders is introduced. The optimization results are complemented with energy dissipation and cell area estimations for a 90 nm CMOS process.     

In-line estimation of the elastic module of milk gels with variation of temperature protein concentration

The cutting time of the curd is a relevant factor to improve the quality of the cheese. Only a few studies have focused on the prediction of objective rheological parameters, such as the elastic modulus of the gel (G′) instead of a subjective cut-off time. A complete randomized factorial design with three replicates was used to determine the effect of proteins and temperature in the prediction of G′ values, gelation time and cutting time in reconstituted skimmed milk gels. The coagulation process was monitored simultaneously using an in-line light backscatter sensor operated at 880 nm and a small amplitude oscillatory rheometer. Changes in the structure of the protein during milk coagulation correlated with the signal changes derived from both the optical sensor and the rheometer. The results showed that the backscatter sensor predicts well (R² = 0.99) the time when the gel reaches a value of G′ = 30 Pa.     

A Discretized Approach to Air Pollution Monitoring Using UAV-based Sensing

Mobile Networks and Applications - Recently, Unmanned Aerial Vehicles (UAVs) have become a cheap alternative to sense pollution values in a certain area due to their flexibility and ability to...     

A framework for conceptual characterization of ontologies and its application in the cybersecurity domain

Software and Systems Modeling - Organizations are actively seeking efficient solutions for the management and protection of their assets. However, Cybersecurity is a vast and complex domain,...     

Alteration of 3D Matrix Stiffness Regulates Viscoelasticity of Human Mesenchymal Stem Cells

Human mesenchymal stem cells (hMSCs) possess potential of bone formation and were proposed as ideal material against osteoporosis. Although interrogation of directing effect on lineage specification by physical cues has been proposed, how mechanical stimulation impacts intracellular viscoelasticity during osteogenesis remained enigmatic. Cyto-friendly 3D matrix was prepared with polyacrylamide and conjugated fibronectin. The hMSCs were injected with fluorescent beads and chemically-induced toward osteogenesis. The mechanical properties were assessed using video particle tracking microrheology. Inverted epifluorescence microscope was exploited to capture the Brownian trajectory of hMSCs. Mean square displacement was calculated and transformed into intracellular viscoelasticity. Two different stiffness of microspheres (12 kPa, 1 kPa) were established. A total of 45 cells were assessed. hMSCs possessed equivalent mechanical traits initially in the first week, while cells cultured in rigid matrix displayed significant elevation over elastic (G′) and viscous moduli (G″) on day 7 (p < 0.01) and 14 (p < 0.01). However, after two weeks, soft niches no longer stiffened hMSCs, whereas the effect by rigid substrates was consistently during the entire differentiation course. Stiffness of matrix impacted the viscoelasticity of hMSCs. Detailed recognition of how microenvironment impacts mechanical properties and differentiation of hMSCs will facilitate the advancement of tissue engineering and regenerative medicine.     

A comparative study of two polyelectrolyte complexes

This study reports on the synthesis and characterization of interpenetrating polymeric network (IPN) and polyelectrolyte complexes (PEC) produced by ion-complex formation between natural and synthetic polymer bearing opposed charge. PEC of sodium alginate (NaAlg) and poly(acryloxyethyl-trimethylammonium chloride-co-2-hydroxyethyl methacrylate) (poly(Q-co-H)) were formed by addition of 2.0 wt % sodium alginate solution to 1.5 wt % poly(Q-co-H) solution, and by adding the poly(Q-co-H) solution to the NaAlg solution under magnetic agitation. The IPN were prepared using the sequential method with three different compositions, in which Q and H monomers were mixed in the 95/5 proportions in presence of NaAlg. The mixture was polymerized at 60°C using potassium persulfate as initiator. The characterizations of scaffolds were investigated by Fourier-transform infrared spectroscopy and thermogravimetric analysis. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012