302 research outputs found
Synthesis and characterization of piezoelectric thin films as functional materials for sensing
This thesis reports about the sputter deposition and characterization of ZnO nanomaterials both in the form of dense and sponge-like thin films. It is shown that high-quality ZnO thin films can be successfully grown on both hard and flexible conductive substrates, with the final aim of proving that their piezoelectric and electrical properties can be successfully exploited in the fabrication of piezoelectric-based nanosensors and nanoactuators. To further state the versatility of ZnO thin films, both spin coated and sputtered dense ZnO thin films were used as seed layers for promoting the growth of well-aligned ZnO nanowires. A strong relationship between the kind of seed layer, i.e., sputtered or spin-coated, and the final NWs morphology, surface chemistry and thus wettability was noticed. In particular NWs grown on sputtered seed layers showed a superhydrophobic behavior, ideal for self-cleaning, anti-fogging or microfluidic devices. In contrast, on spin coated seed layers, highly hydrophilic NWs were obtained, being suitable for further surface functionalization with enhanced adsorption properties towards biological agents or dye for imaging, diagnostic, optical or photovoltaic applications. Finally, the sponge-like morphology is further exploited for the synthesis and characterization of Mn- and Sb- doped, sponge-like ZnO films. The presence of Mn dopant resulted in a high resistance contribution. On the contrary, typical ferroelectric switching phenomena were observed in the Sb-doped ZnO films, showing the presence of hysteretical polarization loops
Gentamicin-releasing mesoporous ZnO structures
Among metal oxides, zinc oxide (ZnO) is one of the most attractive materials thanks to
its biocompatible and biodegradable properties along with the existence of various morphologies
featuring piezoelectric, semiconducting and photocatalytic activities. All of these structures were
successfully prepared and tested for numerous applications, including optoelectronics, sensors and
biomedical ones. In the last case, biocompatible ZnO nanomaterials positively influenced cells growth
and tissue regeneration as well, promoting wound healing and new bone formation. Despite showing
high surface areas, ZnO morphologies generally lack an intrinsic mesoporous structure, strongly
limiting the investigation of the corresponding drug loading and release properties. Within this
scope, this study focuses on the adsorption and release properties of high surface area, mesoporous
ZnO structures using gentamicin sulfate (GS), a well known antibiotic against bacterial infections
especially in orthopedics. The particular ZnO morphology was achieved starting from sputtered
porous zinc layers, finally converted into ZnO by thermal oxidation. By taking advantage of this
mesoporous framework, GS was successfully adsorbed within the ZnO matrix and the kinetic
release profile evaluated for up to seven days. The adsorption of GS was successfully demonstrated,
with a maximum amount of 263 mg effectively loaded per gram of active material. Then, fast kinetic
release was obtained in vitro by simple diffusion mechanism, thus opening further possibilities of
smart pore and surface engineering to improve the controlled delivery
Low-power Secret-key Agreement over OFDM
Information-theoretic secret-key agreement is perhaps the most practically
feasible mechanism that provides unconditional security at the physical layer
to date. In this paper, we consider the problem of secret-key agreement by
sharing randomness at low power over an orthogonal frequency division
multiplexing (OFDM) link, in the presence of an eavesdropper. The low power
assumption greatly simplifies the design of the randomness sharing scheme, even
in a fading channel scenario. We assess the performance of the proposed system
in terms of secrecy key rate and show that a practical approach to key sharing
is obtained by using low-density parity check (LDPC) codes for information
reconciliation. Numerical results confirm the merits of the proposed approach
as a feasible and practical solution. Moreover, the outage formulation allows
to implement secret-key agreement even when only statistical knowledge of the
eavesdropper channel is available.Comment: 9 pages, 4 figures; this is the authors prepared version of the paper
with the same name accepted for HotWiSec 2013, the Second ACM Workshop on Hot
Topics on Wireless Network Security and Privacy, Budapest, Hungary 17-19
April 201
ZnO Nanostructures for Tissue Engineering Applications
This review focuses on the most recent applications of zinc oxide (ZnO) nanostructures for tissue engineering. ZnO is one of the most investigated metal oxides, thanks to its multifunctional properties coupled with the ease of preparing various morphologies, such as nanowires, nanorods, and nanoparticles. Most ZnO applications are based on its semiconducting, catalytic and piezoelectric properties. However, several works have highlighted that ZnO nanostructures may successfully promote the growth, proliferation and differentiation of several cell lines, in combination with the rise of promising antibacterial activities. In particular, osteogenesis and angiogenesis have been effectively demonstrated in numerous cases. Such peculiarities have been observed both for pure nanostructured ZnO scaffolds as well as for three-dimensional ZnO-based hybrid composite scaffolds, fabricated by additive manufacturing technologies. Therefore, all these findings suggest that ZnO nanostructures represent a powerful tool in promoting the acceleration of diverse biological processes, finally leading to the formation of new living tissue useful for organ repair
Porous Zinc Oxide Thin Films: Synthesis Approaches and Applications
Zinc oxide (ZnO) thin films have been widely investigated due to their multifunctional
properties, i.e., catalytic, semiconducting and optical. They have found practical use in a wide number
of application fields. However, the presence of a compact micro/nanostructure has often limited the
resulting material properties. Moreover, with the advent of low-dimensional ZnO nanostructures
featuring unique physical and chemical properties, the interest in studying ZnO thin films diminished
more and more. Therefore, the possibility to combine at the same time the advantages of thin-film
based synthesis technologies togetherwith a high surface area and a porous structuremight represent a
powerful solution to prepare ZnO thin films with unprecedented physical and chemical characteristics
that may find use in novel application fields. Within this scope, this review offers an overview on the
most successful synthesis methods that are able to produce ZnO thin films with both framework and
textural porosities. Moreover, we discuss the related applications, mainly focused on photocatalytic
degradation of dyes, gas sensor fabrication and photoanodes for dye-sensitized solar cells
Development of a Flexible Lead-Free Piezoelectric Transducer for Health Monitoring in the Space Environment
In this work we report on the fabrication process for the development of a flexible piezopolymeric transducer for health monitoring applications, based on lead-free, piezoelectric zinc oxide (ZnO) thin films. All the selected materials are compatible with the space environment and were deposited by the RF magnetron sputtering technique at room temperature, in view of preserving the total flexibility of the structures, which is an important requirement to guarantee coupling with cylindrical fuel tanks whose integrity we want to monitor. The overall transducer architecture was made of a c-axis-oriented ZnO thin film coupled to a pair of flexible Polyimide foils coated with gold (Au) electrodes. The fabrication process started with the deposition of the
bottom electrode on Polyimide foils. The ZnO thin film and the top electrode were then deposited onto the Au/Polyimide substrates. Both the electrodes and ZnO layer were properly patterned by wet-chemical etching and optical lithography. The assembly of the final structure was then obtained by gluing the upper and lower Polyimide foils with an epoxy resin capable of guaranteeing low outgassing levels, as well as adequate thermal and electrical insulation of the transducers. The piezoelectric behavior of the prototypes was confirmed and evaluated by measuring the mechanical displacement induced from the application of an external voltage
Rapid Variability of the accretion disk wind in the narrow line Seyfert 1, PG 1448+273
PG 1448+273 is a luminous, nearby (), narrow line Seyfert 1 galaxy,
which likely accretes close to the Eddington limit. XMM-Newton observations of
PG 1448+273 in 2017 revealed the presence of an ultra fast outflow, as seen
through its blueshifted iron K absorption profile, with an outflow velocity of
about . Here, the first NuSTAR observation of PG 1448+273, performed in
2022 and coordinated with XMM-Newton is presented, which shows remarkable
variability of its ultra fast outflow. The average count rate is a factor of 2
lower during the last 60 ks of the NuSTAR observation, where a much faster
component of the ultra fast outflow was detected with a terminal velocity of
. This is significantly faster than the outflow component which
was initially detected in 2017, when overall PG 1448+273 was observed at a
lower X-ray flux and which implies an order of magnitude increase in the wind
kinetic power between the 2017 and 2022 epochs. Furthermore, the rapid
variability of the ultra fast outflow in 2022, on timescales down to 10 ks,
suggests we are viewing through a highly inhomogeneous disk wind in PG
1448+273, where the passage of a denser wind clump could account for the
increase in obscuration in the last 60 ks of the NuSTAR observation.Comment: 15 pages, 10 figures, accepted for publication in the Astrophysical
Journa
High rejection stacked single-layer graphene membranes for water treatment
Nowadays, the production of pure water from saltwater and wastewater is one of the most challenging issues. Polymeric materials represent, at the moment, the best solution for membranes technology but new materials with improved functionalities are desirable to overcome the typical limitations of polymers. In this work, graphene membranes with superior filtration properties are fabricated by stacking up to three graphene layers on a porous support and exploiting the intrinsic nanopores of graphene to filter diclofenac (drug), and methylene blue (dye). The rejection improves increasing the number of the stacked graphene layers, with the best results obtained with three graphene layers. Mass diffusion properties depend on the size of the probe molecule, consistently with the existence of intrinsic nanometer-sized pores within graphene. From the results of an in depth transmission electron microscopy analysis and molecular dynamics simulations it is inferred that graphene stacking results in a decrease of effective membrane pore sizes to about 13 Ă… diameter which corresponds to 97% rejection for diclofenac and methylene blue after one hour filtration
PERIPHERAL NERVOUS SYSTEM INVOLVEMENT IN LYMPHOPROLIFERATIVE DISORDERS
Peripheral neuropathies are a vast group of diseases with heterogeneous aetiologies, including genetic and acquired causes. Several haematological disorders may cause an impairment of the peripheral nervous system, with diverse mechanisms and variable clinical, electrophysiological and pathological manifestations. In this practical review we considered the main phenotypes of peripheral nervous diseases and examined the haematological disorders which may associate with each of them.
The area of intersection of neurological and haematological fields is of particular complexity and raises several problems in clinical practice. The personal crosstalk between neurologists and haematologists remains a fundamental tool for a proper diagnostic process which may lead to successful treatments in most cases
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