pH-triggered conduction of amine-functionalized single ZnO wire integrated on a customized nanogap electronic platform

The electrical conductance response of single ZnO microwire functionalized with amine-groups was tested upon an acid pH variation of a solution environment after integration on a customized gold electrode array chip. ZnO microwires were easily synthesized by hydrothermal route and chemically functionalized with aminopropyl groups. Single wires were deposited from the solution and then oriented through dielectrophoresis across eight nanogap gold electrodes on a platform single chip. Therefore, eight functionalized ZnO microwire-gold junctions were formed at the same time, and being integrated on an ad hoc electronic platform, they were ready for testing without any further treatment. Experimental and simulation studies confirmed the high pH-responsive behavior of the amine-modified ZnO-gold junctions, obtaining in a simple and reproducible way a ready-to-use device for pH detection in the acidic range. We also compared this performance to bare ZnO wires on the same electronic platform, showing the superiority in pH response of the amine-functionalized material.     

A potential antitumor drug (arginine deiminase) reengineered for efficient operation under physiological conditions

Arginine deiminase (ADI, EC 3.5.3.6) is a potential antitumor drug for the treatment of arginine‐auxotrophic tumors such as hepatocellular carcinomas (HCCs) and melanomas, and studies on human lymphatic leukemia cell lines have confirmed that ADI has antiangiogenic activity. Recent studies showed that a combination of taxane and ADI‐PEG20, which induces caspase‐independent apoptosis, is more effective than taxane monotherapy for prostate cancer. The main limitation of ADI from Pseudomonas plecoglossicida (PpADI) and of many other ADI enzymes lies in their pH‐dependent activity profile. PpADI has a pH optimum at 6.5 and a pH shift from 6.5 to 7.5 results in an ～80 % activity drop (the pH of human plasma is 7.35 to 7.45). In 2010, we reported a proof of concept for ADI engineering by directed evolution that resulted in variant M2 (K5T/D44E/H404R). M2 has a pH optimum of pH 7.0, a fourfold higher k_cat value than the wild‐type PpADI (pH 7.4, 0.5 M phosphate buffer), and an increased K_m value for substrate arginine. In our latest work, variants M5 (K5T/D38H/D44E/A128T/H404R) and M6 (K5T/D38H/D44E/A128T/E296K/H404R) were generated by directed evolution by employing PBS buffer (pH 7.4), which mimics physiological conditions. The S_0.5 value of parent M3 (K5T/D44E/A128T/H404R) decreased from 2.01 to 1.48 mM (M5) and 0.81 mM (M6). The S_0.5 value of M6 (0.81 mM ) is lower than that of wild‐type PpADI (1.30 mM ); the k_cat values improved from 0.18 s^?1 (wild‐type PpADI) to 17.56 s^?1 (M5, 97.6‐fold) and 11.64 s^?1 (M6, 64.7‐fold).     

Directed Evolution of an Antitumor Drug (Arginine Deiminase PpADI) for Increased Activity at Physiological pH

Arginine deiminase (ADI; EC 3.5.3.6) has been studied as a potential antitumor drug for the treatment of arginine‐auxotrophic tumors, such as hepatocellular carcinomas (HCCs) and melanomas. Studies with human lymphatic leukemia cell lines confirmed that ADI is an antiangiogenic agent for treating leukemia. The main limitation of ADI from Pseudomonas plecoglossicida (PpADI) lies in its pH‐dependent activity profile, its pH optimum is at 6.5. A pH shift from 6.5 to 7.5 results in an approximately 80 % drop in activity. (The pH of human plasma is 7.35 to 7.45.) In order to shift the PpADI pH optimum, a directed‐evolution protocol based on an adapted citrulline‐screening protocol in microtiter‐plate format was developed and validated. A proof of concept for ADI engineering resulted in a pH optimum of pH 7.0 and increased resistance under physiological and slightly alkaline conditions. At pH 7.4, variant M2 (K5T/D44E/H404R) is four times faster than the wild‐type PpADI and retains ～50 % of its activity relative to its pH optimum, compared to ～10 % in the case of the wild‐type PpADI.     

Anodic porous alumina structural characteristics study based on SEM image processing and analysis

The present work reports the porous alumina structures fabrication and their quantitative structural characteristics study based on mathematical morphology analysis by using the SEM images. The algorithm used in this work was implemented in 6.2 MATLAB software. Using the algorithm it was possible to obtain the distribution of maximum, minimum and average radius of the pores in porous alumina structures. Additionally, with the calculus of the area occupied by the pores, it was possible to obtain the porosity of the structures. The quantitative results could be obtained and related to the process fabrication characteristics, showing to be reliable and promising to be used to control the pores formation process. Then, this technique could provide a more accurate determination of pore sizes and pores distribution.     

Performance evaluation of sensing fabrics for monitoring physiological and biomechanical variables.

In the last few years, the smart textile area has become increasingly widespread, leading to developments in new wearable sensing systems. Truly wearable instrumented garments capable of recording behavioral and vital signals are crucial for several fields of application. Here we report on results of a careful characterization of the performance of innovative fabric sensors and electrodes able to acquire vital biomechanical and physiological signals, respectively. The sensing function of the fabric sensors relies upon newly developed strain sensors, based on rubber-carbon-coated threads, and mainly depends on the weaving topology, and the composition and deposition process of the conducting rubber-carbon mixture. Fabric sensors are used to acquire the respitrace (RT) and movement sensors (MS). Sensing features of electrodes, instead rely upon metal-based conductive threads, which are instrumental in detecting bioelectrical signals, such as electrocardiogram (ECG) and electromyogram (EMG). Fabric sensors have been tested during some specific tasks of breathing and movement activity, and results have been compared with the responses of a commercial piezoelectric sensor and an electrogoniometer, respectively. The performance of fabric electrodes has been investigated and compared with standard clinical electrodes.     

Scaling Organic Electrochemical Transistors Down to Nanosized Channels

The perspective of downscaling organic electrochemical transistors (OECTs) in the nanorange is approached by depositing poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) on electrodes with a nanogap designed and fabricated by electromigration induced break junction (EIBJ) technique. The electrical response of the fabricated devices is obtained by acquiring transfer characteristics in order to clarify the specific main characteristics of OECTs with sub‐micrometer‐sized active channels (nanogap‐OECTs). On the basis of their electrical response to different scan times, the nanogap‐OECT shows a maximum transconductance unaffected upon changing scan times in the time window from 1 s to 100 µs, meaning that fast varying signals can be easily acquired with unchanged amplifying performance. Hence, the scaling down of the channel size to the nanometer scale leads to a geometrical paradigm that minimizes effects on device response due to the cationic diffusion into the polymeric channel. A comprehensive study of these features is carried out by an electrochemical impedance spectroscopy (EIS) study, complemented by a quantitative analysis made by equivalent circuits. The propagation of a redox front into the polymer bulk due to ionic diffusion also known as the “intercalation pseudocapacitance” is identified as a limiting factor for the transduction dynamics.     

Recommendations for mass spectrometry data quality metrics for open access data (corollary to the Amsterdam principles)

Policies supporting the rapid and open sharing of proteomic data are being implemented by the leading journals in the field. The proteomics community is taking steps to ensure that data are made publicly accessible and are of high quality, a challenging task that requires the development and deployment of methods for measuring and documenting data quality metrics. On September 18, 2010, the U.S. National Cancer Institute (NCI) convened the "International Workshop on Proteomic Data Quality Metrics" in Sydney, Australia, to identify and address issues facing the development and use of such methods for open access proteomics data. The stakeholders at the workshop enumerated the key principles underlying a framework for data quality assessment in mass spectrometry data that will meet the needs of the research community, journals, funding agencies, and data repositories. Attendees discussed and agreed up on two primary needs for the wide use of quality metrics: (i) an evolving list of comprehensive quality metrics and (ii) standards accompanied by software analytics. Attendees stressed the importance of increased education and training programs to promote reliable protocols in proteomics. This workshop report explores the historic precedents, key discussions, and necessary next steps to enhance the quality of open access data. By agreement, this article is published simultaneously in Proteomics, Proteomics Clinical Applications, Journal of Proteome Research, and Molecular and Cellular Proteomics, as a public service to the research community. The peer review process was a coordinated effort conducted by a panel of referees selected by the journals.     

Hybrid multi-attribute QoS optimization in component based software systems

Design decisions for complex, component-based systems impact multiple quality of service (QoS) properties. Often, means to improve one quality property deteriorate another one. In this scenario, selecting a good solution with respect to a single quality attribute can lead to unacceptable results with respect to the other quality attributes. A promising way to deal with this problem is to exploit multi-objective optimization where the objectives represent different quality attributes. The aim of these techniques is to devise a set of solutions, each of which assures an optimal trade-off between the conflicting qualities. Our previous work proposed a combined use of analytical optimization techniques and evolutionary algorithms to efficiently identify an optimal set of design alternatives with respect to performance and costs. This paper extends this approach to more QoS properties by providing analytical algorithms for availability-cost optimization and three-dimensional availability-performance-cost optimization. We demonstrate the use of this approach on a case study, showing that the analytical step provides a better-than-random starting population for the evolutionary optimization, which lead to a speed-up of 28% in the availability-cost case.     

Biometrics from brain electrical activity: a machine learning approach

The potential of brain electrical activity generated as a response to a visual stimulus is examined in the context of the identification of individuals. Specifically, a framework for the visual evoked potential (VEP)-based biometrics is established, whereby energy features of the gamma band within VEP signals were of particular interest. A rigorous analysis is conducted which unifies and extends results from our previous studies, in particular, with respect to 1) increased bandwidth, 2) spatial averaging, 3) more robust power spectrum features, and 4) improved classification accuracy. Simulation results on a large group of subject support the analysis     

On the feasibility of IEEE 802.11 multi-channel multi-hop mesh networks

Several scientific works have considered the possibility to build Wireless Mesh Networks (WMN) using multi-channel IEEE 802.11 architectures. At the basis of these works is the notion of “non-overlapping” channels, i.e. with a frequency separation equal or greater than 25 MHz. It is now a common assumption that multiple independent transmissions over these channels can coexist without mutual interference even in physical proximity. In this work we demonstrate that this assumption does not hold in general. Through an extensive set of experiments we illustrate the presence of cross-channel interference between “non-overlapping” channels at relay nodes due to the “near-far” effect. We analyze in what manner the MAC layer reacts to such an interference and how this problem extends to higher layers, with detrimental effects on the global throughput. The central problem is that cross-channel interference is not handled adequately by the MAC layer, and in some cases single-channel multi-hop settings perform better than multi-channel. Our results highlight a serious mismatch between some routing and channel assignment schemes proposed recently by the research community, assuming full separation between non-overlapping channels, and what is achievable in practice. More generally, as the presence of cross-channel interference can not be neglected at relay nodes, our findings point to a fundamental problem in building Multi-channel Multi-hop WMN based on IEEE 802.11b/g technology.