Cellular Deformations Induced by Conical Silicon Nanowire Arrays Facilitate Gene Delivery

Engineered cell–nanostructured interfaces generated by vertically aligned silicon nanowire (SiNW) arrays have become a promising platform for orchestrating cell behavior, function, and fate. However, the underlying mechanism in SiNW‐mediated intracellular access and delivery is still poorly understood. This study demonstrates the development of a gene delivery platform based on conical SiNW arrays for mechanical cell transfection, assisted by centrifugal force, for both adherent and nonadherent cells in vitro. Cells form focal adhesions on SiNWs within 6 h, and maintain high viability and motility. Such a functional and dynamic cell–SiNW interface features conformational changes in the plasma membrane and in some cases the nucleus, promoting both direct penetration and endocytosis; this synergistically facilitates SiNW‐mediated delivery of nucleic acids into immortalized cell lines, and into difficult‐to‐transfect primary immune T cells without pre‐activation. Moreover, transfected cells retrieved from SiNWs retain the capacity to proliferate—crucial to future biomedical applications. The results indicate that SiNW‐mediated intracellular delivery holds great promise for developing increasingly sophisticated investigative and therapeutic tools.     

Amphoteric hydrogels for immobilization of enzymes using template polymerization technique

Novel ionizable amphoteric hydrogels were prepared from poly(acrylic acid) and dimethylaminoethyl methacrylate monomer, employing template polymerization technique. The mode of interaction, as proved by FTIR, was multiple H‐bonding between the tertiary amino group of the monomer and the carboxylic groups of the polymer. The impact of varying equal polymer–monomer feed ratios from 0.1 to 1.1 on the swelling dynamics was examined. Penetrant sorption experiments demonstrated that the swelling behavior depends strongly on the polymer complex composition. The polymer complex of feed ratio 0.5 : 0.5 (polymer : monomer) showed maximum swelling percentage. The mechanism of the polymer complexes swelling was probably a non‐Fickian with n values approaching Fickian behavior. The hydrogels showed maximum swelling efficiencies of 27 folds and 13.5 folds in drastic acidic and basic medium, respectively, using polymer complex of 0.5 : 0.5 feed ratio. Because of reversibility and rapidity of swelling, the gel could be considered as a mechanochemical system. The prepared hydrogel successfully immobilized the industrially used β‐galactosidase as an acidic model enzyme. The novel immobilized enzyme showed a remarkable improvement in its activity (13.8 μmol min^?1 mg^?1) compared to the free enzyme (3.2 μmol min^?1 mg^?1). The optimum pH values for free and immobilized enzyme were 4.5–5 and 4, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Analysis of Priority R‐ALOHA (PR‐ALOHA) protocol

With the exception of required time synchronization, the Reservation‐ALOHA (R‐ALOHA) protocol is simple to implement and suitable for medium access control in ad hoc wireless networks. In this paper, we propose an innovative protocol, referred to as Reservation ALOHA with priority (PR‐ALOHA) that provides differentiated services on the basis of traffic priority. To date, the carrier sense multiple access/collision avoidance (CSMA/CA) protocol has been widely used for this purpose by employing an interframe spacing (IFS) for priority service, that is, nodes ready for packet transmissions are required to wait for an IFS amount of time, where a shorter IFS is used to gain faster access to the radio channel. However, sensing and collision avoidance mechanisms make CSMA/CA unsuitable for delay‐sensitive applications, that is, congested scenarios with high traffic. In contrast, the proposed PR‐ALOHA protocol may be considered a good candidate for such applications. In this paper, the performance of the PR‐ALOHA protocol is investigated analytically and by simulation. Its comparison with regular R‐ALOHA is also carried out. Modeling and simulation results of PR‐ALOHA show that PR‐ALOHA improves the performance of high‐priority traffic with limited effect on normal network traffic. Thus, PR‐ALOHA may be useful in vehicular communications, where traffic may be separated into emergency messages having high priority and multimedia messages having low priority. Copyright © 2013 John Wiley & Sons, Ltd.     

A 1.8 V low power 5 Gbps PMOS-based LVDS output driver with good return loss performance

This paper presents a novel design topology of a 5 Gbps PMOS-based low voltage differential signaling (LVDS) voltage mode output driver. The topology is designed to meet the requirements of low power consumption and high data rates applications. The driver consists of an output stage and a pre-driver stage where the driver’s swing and common-mode output voltage are set. The pre-driver and the output stage consume only 13.1 mW of power at 5 Gbps speed while operating from a 1.8 V voltage supply. Further, the design achieved ?21 dB return loss performance at DC. The driver was extracted and simulated using Mentor Graphics CAD tools and implemented in 180 nm CMOS technology. The output signal is fully compliant with the LVDS standard output swing and common-mode voltage specifications.     

Opportunistic channel allocation decision making in cognitive radio communications

The global spread of wireless devices with mobile Internet access and the increasing demand of multimedia‐based applications are fueling the need for wireless broadband networks. IEEE 802.16 and 802.20 are standards for a broadband wireless access with promising cognitive radio features to support mobile Internet access. However, because of the fast changing radio environment and the demand for dynamic spectrum allocation mechanisms, these standards must continuously readjust different radio parameters. The cognitive radio makes decisions based on its built‐in inference engine, which also in time can adapt itself to different situations through the process of learning from experience. In this paper we present an automated opportunistic decision making and learning process for cognitive radio based on uncertainty reasoning algorithms. This novel approach is well suited in fast changing wireless environments with vague, incomplete, and heterogeneous information. Theory and simulations prove that decision making and learning of the cognitive radio based on the proposed approach cope with the changes in the radio environment. In this work we use fuzzy logic for the learning and decision making of the cognitive radio. Simulation also show that our approach provides accurate and precise decisions on allocating spectrum to mobile Internet users even in fast varying radio conditions. Copyright © 2012 John Wiley & Sons, Ltd.     

Accurate 3D action recognition using learning on the Grassmann manifold

In this paper we address the problem of modeling and analyzing human motion by focusing on 3D body skeletons. Particularly, our intent is to represent skeletal motion in a geometric and efficient way, leading to an accurate action–recognition system. Here an action is represented by a dynamical system whose observability matrix is characterized as an element of a Grassmann manifold. To formulate our learning algorithm, we propose two distinct ideas: (1) in the first one we perform classification using a Truncated Wrapped Gaussian model, one for each class in its own tangent space. (2) In the second one we propose a novel learning algorithm that uses a vector representation formed by concatenating local coordinates in tangent spaces associated with different classes and training a linear SVM. We evaluate our approaches on three public 3D action datasets: MSR-action 3D, UT-kinect and UCF-kinect datasets; these datasets represent different kinds of challenges and together help provide an exhaustive evaluation. The results show that our approaches either match or exceed state-of-the-art performance reaching 91.21% on MSR-action 3D, 97.91% on UCF-kinect, and 88.5% on UT-kinect. Finally, we evaluate the latency, i.e. the ability to recognize an action before its termination, of our approach and demonstrate improvements relative to other published approaches.