Inorganic–organic hybrid materials with zirconium oxoclusters as protective coatings on aluminium alloys

Inorganic–organic hybrid materials are attracting a strong scientific interest mainly for their outstanding inherent mechanical and thermal properties, which can be traced back to the intimate coupling of both inorganic and organic components. By carefully choosing the experimental parameters used for their synthesis, chemically and thermally stable acrylate-based hybrid material embedding the zirconium oxocluster Zr₄O₄(OMc)₁₂, where OMcCH₂C(CH₃)C(O)O, can be deposited as UV-cured films on aluminium alloys.

In particular, the molar ratios between the oxocluster and the monomer, the polymerisation time, the amount of photo-initiator and the deposition conditions, by using an home-made spray-coating equipment, were optimised in order to obtain the best performing layers in terms of transparency and hardness to coat aluminium alloy (AA1050, AA6060 and AA2024) sheets. Furthermore, it was also evaluated whether the hybrid coatings behave as barrier to corrosion.

Several coated samples were prepared and characterised. Environmental scanning electronic microscopy (ESEM) and scratch test were used to investigate the morphology of the films and to evaluate their scratch resistance, respectively. Electrochemical impedance spectroscopy (EIS) was performed in order to evaluate if the coatings actually protect the metallic substrate from corrosion.

In order to measure shear storage modulus (G′) and loss modulus (G″) of the materials used for coatings, bulk samples were also obtained by UV-curing of the precursors solution. Dynamical mechanical thermal analysis (DMTA) was performed in shear mode on cured disks of both the hybrid materials and pristine polymer for comparison. The values of T_g were read off as the temperatures of peak of loss modulus. The length and mass of all the samples were measured before and after the DMTA analysis, so that the shrinkage of the materials in that temperature range was exactly evaluated.     

Tissue Engineering and Regenerative Medicine in Pediatric Urology: Urethral and Urinary Bladder Reconstruction

In the case of pediatric urology there are several congenital conditions, such as hypospadias and neurogenic bladder, which affect, respectively, the urethra and the urinary bladder. In fact, the gold standard consists of a urethroplasty procedure in the case of urethral malformations and enterocystoplasty in the case of urinary bladder disorders. However, both surgical procedures are associated with severe complications, such as fistulas, urethral strictures, and dehiscence of the repair or recurrence of chordee in the case of urethroplasty, and metabolic disturbances, stone formation, urine leakage, and chronic infections in the case of enterocystoplasty. With the aim of overcoming the issue related to the lack of sufficient and appropriate autologous tissue, increasing attention has been focused on tissue engineering. In this review, both the urethral and the urinary bladder reconstruction strategies were summarized, focusing on pediatric applications and evaluating all the biomaterials tested in both animal models and patients. Particular attention was paid to the capability for tissue regeneration in dependence on the eventual presence of seeded cell and growth factor combinations in several types of scaffolds. Moreover, the main critical features needed for urinary tissue engineering have been highlighted and specifically focused on for pediatric application.     

DAWL: A Delayed-ACK Scheme for MAC-Level Performance Enhancement of Wireless LANs

The IEEE 802.11 MAC protocol provides a reliable link layer using Stop & Wait ARQ. The cost for high reliability is the overhead due to acknowledgement packets in the direction opposite to the actual data flow. In this paper, the design of a new protocol as an enhancement of IEEE 802.11 is proposed, with the aim of reducing supplementary traffic overhead and increasing the bandwidth available for actual data transmission. The performance of the proposed protocol is evaluated through comparison with IEEE 802.11 as well as with a SSCOP-based protocol. Results underline significant advantages of the proposed protocol against existing ones, thus confirming the value and potentiality of the approach.Dzmitry Kliazovich received his Masters degree in telecommunication science from Belarusian State University of Informatics and Radioelectronics in 2002. He is currently working towards the Ph.D. degree in University of Trento, Italy. His main research interest lies in wireless networking field with a focus on performance optimization and cross-layer design.Fabrizio Granelli was born in Genoa in 1972. He received the “Laurea” (M.Sc.) degree in Electronic Engineering from the University of Genoa, Italy, in 1997, with a thesis on video coding, awarded with the TELECOM Italy prize, and the Ph.D. degree in Electronic Engineering and Computer Science from the same university in 2001. Since 2000 he is carrying on his teaching activity as Assistant Professor at the Dept. of Information and Communication Technologies (DIT) of the University of Trento (Italy) within the B.Sc. and M.Sc. Degrees in Telecommunications Engineering.The research interests of Dr. Granelli are mainly focused on networking, with particular attention to network modeling and performance evaluation, wireless networks, access control, and next-generation telecommunication networks.He is author of more than 30 refereed papers, published in several international journals and conferences.Dr. Granelli is member of the IEEE Committee on “Communication Systems Integration and Modeling” (CSIM) and of the Technical Programme Committee of the “QoS and Performance Evaluation Symposium” of the International Conference on Communications (ICC 2003 and ICC 2004).     

Noninvasive ECG as a tool for predicting termination of paroxysmal atrial fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia and entails an increased risk of thromboembolic events. Prediction of the termination of an AF episode, based on noninvasive techniques, can benefit patients, doctors and health systems. The method described in this paper is based on two-lead surface electrocardiograms (ECGs): 1-min ECG recordings of AF episodes including N-type (not terminating within an hour after the end of the record), S-type (terminating 1 min after the end of the record) and T-type (terminating immediately after the end of the record). These records are organised into three learning sets (N, S and T) and two test sets (A and B). Starting from these ECGs, the atrial and ventricular activities were separated using beat classification and class averaged beat subtraction, followed by the evaluation of seven parameters representing atrial or ventricular activity. Stepwise discriminant analysis selected the set including dominant atrial frequency (DAF, index of atrial activity) and average HR (HRmean, index of ventricular activity) as optimal for discrimination between N/T-type episodes. The linear classifier, estimated on the 20 cases of the N and T learning sets, provided a performance of 90% on the 30 cases of a test set for the N/T-type discrimination. The same classifier led to correct classification in 89% of the 46 cases for N/S-type discrimination. The method has shown good results and seems to be suitable for clinical application, although a larger dataset would be very useful for improvement and validation of the algorithms and the development of an earlier predictor of paroxysmal AF spontaneous termination time.     

Optical micro-structures fabricated on top of optical fibers by means of two-photon photopolymerization

In this work we report, for the first time to our knowledge, the possibility to fabricate various structures, with good optical proprieties, on the top of optical fibers, using the two-photon lithography (TPL) technique. We show the convenience of this approach to quickly create generic 3D shapes using a single set-up by contrast to past shape-dependent methods. A set of different structures are fabricated and characterized to demonstrate the versatility of this approach and their high optical quality.     

Ultrahydrophobic PMMA micro- and nano-textured surfaces fabricated by optical lithography and plasma etching for X-ray diffraction studies

Polymeric (PMMA) ultrahydrophobic surfaces with contact angles up to about 170° have been fabricated and used in the context of synchrotron radiation experiments on biological droplets. The different microfabrication processes included either an optical lithography phase followed by a plasma texturing one or a single step deep reactive ion etch attack.The drying of several biological solution droplets has been monitored. Room temperature evaporation experiments (lysozyme, lactalbumin, cytochrome C, doxorubicin and synthesized peptides) finally result in the formation of easily detachable hollow residuals because of the low interaction between the ultrahydrophobic substrate and the aqueous droplet while pilot experiments (bovine insulin) in a sitting-drop environment bring to the formation of well defined crystals. Recent results about in situ X-ray diffraction experiments by SAXS & WAXS (Small and Wide Angle X-ray Scattering) μ-beam techniques confirm that the presence of such surfaces influences the formation of crystal or fibril structures. These substrates represent indeed a suitable support to study biological and inorganic droplets in a near contact-free environment exploiting the homogeneous evaporation rate induced by the ultrahydrophobicity of the system.     

Comparative analysis of the outdoor performance of a dye solar cell mini‐panel for building integrated photovoltaics applications

New generation photovoltaic (PV) devices such as polymer and dye sensitized solar cells (DSC) have now reached a more mature stage of development, and among their various applications, building integrated PVs seems to have the most promising future, especially for DSC devices. This new generation technology has attracted an increasing interest because of its low cost due to the use of cheap printable materials and simple manufacturing techniques, easy production, and relatively high efficiency. As for the more consolidated PV technologies, DSCs need to be tested in real operating conditions and their performance compared with other PV technologies to put into evidence the real potential. This work presents the results of a 3 months outdoor monitoring activity performed on a DSC mini‐panel made by the Dyepower Consortium, positioned on a south oriented vertical plane together with a double junction amorphous silicon (a‐Si) device and a multi‐crystalline silicon (m‐Si) device at the ESTER station of the University of Rome Tor Vergata. Good performance of the DSC mini‐panel has been observed for this particular configuration, where the DSC energy production compares favorably with that of a‐Si and m‐Si especially at high solar angles of incidence confirming the suitability of this technology for the integration into building facades. This assumption is confirmed by the energy produced per nominal watt‐peak for the duration of the measurement campaign by the DSC that is 12% higher than that by a‐Si and only 3% lower than that by m‐Si for these operating conditions. Copyright © 2013 John Wiley & Sons, Ltd.     

SVD-Based Techniques for Zero-Padded Block Transmission Over Fading Channels

In this paper, the performance of filter bank transceivers in the presence of a dispersive time-variant channel is investigated. It is well known that filter bank transceivers can be adapted to the channel transfer function to yield intersymbol interference (ISI) cancellation. When the channel is time variant, several problems arise, since the transceiver should be changed whenever the channel evolves. In this paper, we will allow both the transmitter and the receiver to change and satisfy the interference-free condition, under the assumption of a zero-padded block transmission. In this case, the optimum transmitter-receiver pair can be computed by using a singular value decomposition (SVD) of the channel matrix. A fast receiver adaptation based on SVD tracking is presented. Simulation results show that minimum performance loss with respect to the optimum receiver can be achieved for our reduced complexity receiver     

A Transmit and Receive Multi-Antenna Channel Model and Simulator for Communications from High Altitude Platforms

The interest of the scientific and industrial communities on the application of high altitude stratospheric platforms to communications is increasingly growing. Several research projects and field trials are being carried out by international consortia and specific portions of the electromagnetic spectrum have been allocated by the International Telecommunications Union (ITU) for communications applications. The channel experienced by such systems plays a key role for the provision of reliable communications services but, unfortunately, its inherent characteristics are substantially different from those of other channel typologies. Therefore, in order to design and simulate effective propagation impairment mitigation techniques such as adaptive modulation and coding or adaptive beamforming and equalization algorithms, an ad hoc channel model and simulator is definitively required. In this paper a novel channel model and a related channel simulator especially tailored for HAP-based communication systems are presented. The model is conceived for link-level simulations of point-to-point communication links, wherein both the transmitter and the receiver may be equipped with an array of antennas. Peculiar physical effects of the stratospheric channel are taken into account as well as impairments due to the possible presence of scatterers and relative movement of both transmitting and receiving stations. The structure of the channel simulator has been conceived to maintain the computational burden at required by the channel simulator is kept low by an efficient tapped delay line implementation. This work is supported by the CAPANINA project (FP6 IST-2003-506745): Communications from aerial platform networks delivering broadband communications for all, http://www.capanina.org.

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Double actuation architectures for rendering variable impedance in compliant robots: A review

Novel compliant actuation systems have been developed in recent years for a variety of possible advantages, such as establishing a safe human–robot interaction, increasing energy efficiency, reducing the effects of impacts and even for the development of neuro-inspired robotic platforms to be used in human motor control studies.In this rapidly growing and transversal research field, systems involving more than one active element (typically motors) for each actuated degree of freedom are being investigated to allow separate position and impedance regulations. Considering the wide range of applications and the large number of different arrangements deriving from the combination of two active elements and passive elastic components, several actuation architectures have been devised.This paper reviews state-of-the-art rotary variable impedance units incorporating two separate motors. Existing devices are grouped in three main categories. A critical and comparative analysis of the most relevant features is carried out, also based on most representative prototypes. Recently proposed methodologies and evaluation criteria for design optimization are illustrated and perspectives on potential applications of double actuation systems are presented.