PERSPECTIVE
published: 22 March 2016
doi: 10.3389/fenvs.2016.00020
Frontiers in Environmental Science | www.frontiersin.org 1 March 2016 | Volume 4 | Article 20
Edited by:
Md Ahmaruzzaman,
National Institute of Technology
Silchar, India
Reviewed by:
Matteo Guidotti,
Institute of Molecular Science and
Technologies - National Research
Council, Italy
Alexei Lapkin,
University of Cambridge, UK
*Correspondence:
Leonardo F. Fraceto
leonardo@sorocaba.unesp.br
Specialty section:
This article was submitted to
Green and Environmental Chemistry,
a section of the journal
Frontiers in Environmental Science
Received: 22 January 2016
Accepted: 07 March 2016
Published: 22 March 2016
Citation:
Fraceto LF, Grillo R, de Medeiros GA,
Scognamiglio V, Rea G and
Bartolucci C (2016) Nanotechnology
in Agriculture: Which Innovation
Potential Does It Have?
Front. Environ. Sci. 4:20.
doi: 10.3389/fenvs.2016.00020
Nanotechnology in Agriculture:
Which Innovation Potential Does It
Have?
Leonardo F. Fraceto
1
*
, Renato Grillo
2
, Gerson A. de Medeiros
1
, Viviana Scognamiglio
3
,
Giuseppina Rea
3
and Cecilia Bartolucci
3, 4
1
Department of Environmental Engineering, São Paulo State University, Sorocaba, Brazil,
2
Center of Natural and Human
Sciences, Federal University of ABC, Santo André, Brazil,
3
Institute of Crystallography, National Research Council, Rome,
Italy,
4
Science and Technology Foresight, National Research Council, Rome, Italy
Recent scientific data indicate that nanotechnology has the potential to positively impact
the agrifood sector, minimizing adverse problems of agricultural practices on environment
and human health, improving food security and productivity (as required by the predicted
rise in global population), while promoting social and economic equity. In this context, we
select and report on recent trends in nanomaterial-based systems and nanodevices that
could provide benefits on the food supply chain specifically on sustainable intensification,
and management of soil and waste. Among others, nanomaterials for controlled-release
of nutrients, pesticides and fertilizers in crops are described as well as nanosensors for
agricultural practices, food quality and safety.
Keywords: nanotechnology, nanodelivery systems, nanosensors, sustainable agriculture
CURRENT AND FUTURE TRENDS
Recently, a wide range of potential applications of nanotechnology has been envisaged also in
agriculture, leading to intense research at both academic and industrial levels (
Chen and Yada, 2011;
Dasgupta et al., 2015; Parisi et al., 2015). Indeed, the unique properties of materials at nanoscale
make them suitable candidates for the design and development of novel tools in support of a
sustainable agriculture. Some of the main applications of these nanotools in agriculture are reported
in the following paragraphs, and schematically drawn in Figure 1.
Systems for Sustainable Intensification in Agriculture
Sustainable intensification is a concept related to a production system aiming to increase
the yield without adverse environmental impact while cultivating t he same agricultural area
(The Royal Society, 2009). This paradigm provides a framework to evaluate the selection of
the best combination of approaches to agricultural production considering the influence of the
current biophysic al, social, cultural, and economic situation (Garnett and Godfray, 2012). In this
context, novel nanomaterials based on the use of inorganic, polymeric, and lipid nanoparticles,
synthesized by exploiting different techniques (e.g., emulsification, ionic gelation, polymerization,
oxydoreduction, etc) have been developed to increase productivity (Figure 1A).
They can find application, as an example, for the development of intelligent nanosystems for the
immobilization of nutrients and their release in soil. Such systems have the advantage to minimize
leaching, while improving the uptake of nutrients by plants, and to mitigate eutrophication
by reducing the transfer of nitrogen to groundwater (
Liu and Lal, 2015). Furthermore, it
is noteworthy to mention that nanomaterials could also be exploited to improve structure
and function of pesticides by increasing solubility, enhancing resistance against hydrolysis
Fraceto et al. Applications of Nanotechnology in Agriculture
FIGURE 1 | Potential applications of nanotechnology in agriculture. (A) Increase the productivity using nanopesticides and nanofertilizers; (B) Improve the
quality of the soil using nanozeolites and hydrogels; (C) Stimulate plant growth using nanomaterials (SiO
2
, TiO
2
, and carbon nanotubes); (D) Provide smart monitoring
using nanosensors by wireless communication devices.
and photodecomposition, and/or by providing a more specific
and controlled-release toward target organisms (Mishra and
Singh, 2015; Grillo et al., 2016; Nuruzzaman et al., 2016).
Systems to Improve the Quality of the Soil
Hydrogels, nanoclays, and nanozeolites have been reported to
enhance the water-holding capacity of soil (Sekhon, 2014), hence
acting as a slow release source of water, reducing the hydric
shortage periods during crop season (Figure 1B). Applications
of such systems are favorable for both agricultural purposes and
reforestation of degraded areas. Organic e.g., such as polymer
and carbon nanotubes and inorganic e.g., such as nano metals
and metal oxides nanomaterials have also been used to absorb
environmental contaminants (Khin et al., 2012), increasing
soil remediation capacity and reducing times and costs of t he
treatments.
Nanomaterials as Agents to Stimulate
Plant Growth
Carbon nanotubes and nanoparticles of Au, SiO
2
, ZnO, and
TiO
2
can contribute to ameliorate development of plants
(Figure 1C), by enhancing elemental upta ke and use of nutrients
(
Khot et al., 2012). However, the real impact of nanomaterials
on plants depends on their composition, concentration, size,
surface charge, and physical chemical properties, besides the
susceptibility of the plant species (
Ma et al., 2010; Lambreva et al.,
2015
). The development of new protocols and the use of different
analytical techniques (such as microscopy, magnetic resonance
imaging, and fluorescence spectroscopy) could considerably
contribute to understand the interactions between plants and
nanomaterials.
Nano-d for the Management of the Food
Supply Chain
Nanotechnology can find applications also in the development of
analytical devices dedicated to the control of quality, bio/security,
and safety not only in agriculture, but also along the food supply
chain (
Valdes et al., 2009). In this context, nanosensors represent
a powerful tool with advanced and improved fea tures, compared
to existing analytical sensors and biosensors. Nanosensors
are defined as analytical devices having at least one sensing
dimension no greater than 100 nm, fabricated for monitoring
physico-chemical properties in places otherwise difficult to
reach. Nanotubes, nanowires, nanoparticles, or nanocrystals are
often used to optimize the signal transduction deriving by
sensing elements in response to exposure to biological and
chemical analytes having similar size. They have unique surface
chemistry, distinct thermal, ele c trical and optical properties,
useful to enhance sensitivities, reduce response times, and
improve detection limits, and can be used in multiplexed systems
(
Aragay et al., 2010; Yao et al., 2014). Considering the huge
Frontiers in Environmental Science | www.frontiersin.org 2 March 2016 | Volume 4 | Article 20
Fraceto et al. Applications of Nanotechnology in Agriculture
amount of research in thi s area, real applications of nanosensors
for field analysis are unexpectedly scarce, implying the potential
for a new market. In this perspective, nanotechnologies could
enhance biosensor performance to allow real applications in
agrifood (Figure 1D). Indeed, thanks to important progresses
in nanofabrication, laboratory analytical techniques, such as
surface plasmon resonance, mass spectrometry, chromatography,
or electrophoresis chips, can support the development of viable
sensor components. However, the real need of the market
is the realization of automated embedded systems, which
integrate biosensing components with micro/nanofluidics, data
management hardware, and remote control by wireless networks.
This is a key issue for nanotechnology, which can provide
the decisive approaches as well as novel nanomaterials for the
realization of biosensing devices (Scognamiglio, 2013). Indeed,
as described by Mousavi and Rezaei (2011) “Nanosensors
help farmers in maintaining farm with precise control and
report timely needs of plants.” Thus, it will be mandatory to
address research efforts to the development of nanosensors to
aid decision-making in crop monitoring, accurate analysis of
nutrients and pesticides in soil, or for maximizing the efficiency
of water use for a smart agriculture. In this context, nanosensors
could demonstrate their potential in managing all the phases
of the food supply chain, from crop cultivation and harvesting
to food processing, transportation, packaging, and distribution
(
Scognamiglio et al., 2014). Among them, nanosensors for
dynamic measurement of soil parameters (pH and nutrients,
residual pesticides in crop and soil, and soil humidity) detection
of pathogens and prediction of nitrogen uptake are only few
examples to foster a sustainable farming (Bellingham, 2011).
Specifically, nanosensor systems can be developed to monitor
the presence of pests, pathogens or pesticides in order to
better tune the amount of insecticides to be employed for crop
productivity management, since they show higher sensitivity
and specificity compared to the “traditional” sensors. For
example, controlled release me chanisms via nanoscale carriers
monitored by nanosensors integrated in platforms employing
wireless signals, will avoid overdose of agricultural chemicals
and minimize inputs of fertilizers and pesticides during the
course of cultivations, improving productivity, and reducing
waste. Networks of nanosensors located throughout cultivated
fields will assure a real time and comprehensive monitoring of
the crop growt h, furnishing effective high quality data for best
management practices (El Beyrouthya and El Azzi, 2014).
The automation of irrigation systems is a lso a crucial
requirement of smart agriculture, mainly in a scenario of water
shortage. In this regard, sensor technology has the potential to
maximize the efficiency of water use. Nanosensors estimating
soil water tension in real-time may be coupled with autonomous
irrigation controllers. This feature allows a sustainable irrigation
management based on drying soil, otherwise an approach too
difficult for farmers because it involves evaluation of climate and
crop growth aspects of high complexity (de Medeiros et al., 2001).
Furthermore, nanosensors find also application in fast,
sensitive, and cost-effective detection of different targets
to ensure food quality, safety, freshness, authenticity, and
traceability along the entire food supply chain. Surely,
nanosensors represent one of the emerging technologies
challenging the assessment of food quality and s afety, being able
to provide smart monitoring of food components (e.g., sugars,
amino acid, alcohol, vitamins, and minerals) and contaminants
(e.g., pesticides, heavy metals, toxins, and food additives). Food
quality and food safety control represents a crucial effort not
only to obtain a healthy food, but also to avoid huge waste
of food products. The potential of nanosensor can also be
demonstrated by the last trends on intelligent or smart packaging
to monitor the freshness properties of food, and check the
integrity of the packages during transport, storage, and display
in markets (
Vanderroost et al., 2014). Many intelligent packaging
involve nanosensors as monitoring systems to measure physical
parameters (humidity, pH, temperature, light exposure), to
reveal gas mixtures (e.g., oxygen and c ar bon dioxide), to detect
pathogens and toxins, or to control freshness (e.g., ethanol,
lactic acid, acetic acid) and decomposition (e.g., putrescine,
cadaverine).
IDENTIFICATION OF GAPS AND
OBSTACLES
Despite considerable advances in identifying possible
applications of nanotechnology in agriculture, many issues
remain to be resolved in the near future before this technology
may make significant contributions to the area of agriculture.
Some of the main aspects that require further attention are:
(i) development of specific hybrid carriers for delivering active
agents including nutrients, pesticides and fertilizers in order
to maximize their efficiency following the principles of green
chemistry and environmental sustainability (
De Oliveira et al.,
2014); (ii) design of processes easily upscalable at industrial level,
(iii) comparison of effects of nanoformulations/nanosystems
with existing commercia l products, in order to demonstrate
real practical advantages; (iv) acquisition of knowledge and
developments of methods for risk and life-cycle assessment
of nanomaterials, nanopesticides, nanofertilizers, as well as
assessment of the impacts (e.g., phytotoxic effects) on non-target
organisms e.g., other plants, soil mic robiota, and bees; (v)
advances in t he regulations about the use of nanomaterials
(Amenta et al., 2015). In this context, the progress made in the
exploitation of nanopesticides (such as atrazine) represents a
useful case study to identify the main parameters necessary to
predict the behavior of nanomaterials in the environment (Grillo
et al., 2012). In the study of the atrazine-nanopesticide system
care was taken to understand the mechanisms of interaction
with both target, mustard (Oliveira et al. , 2015a), and non-target
organisms, maize (Oliveira et al., 2015b), and risk-assessment
analyses were also considered (Kah et al., 2014). However,
future case studies are necessary in order to address the safety
of workers and consumers with respect to food produced using
nanomaterials and nanoparticles (Figure 2).
The implementation of nanotechnology in agriculture
requires also the development of techniques capable of
quantifying engineered nanoparticles at the concentrations
present in different environmental compartments (
Sadik et al.,
Frontiers in Environmental Science | www.frontiersin.org 3 March 2016 | Volume 4 | Article 20
Fraceto et al. Applications of Nanotechnology in Agriculture
FIGURE 2 | Timescale for developments in atrazine nanopesticide.
2014). Currently available methods are not always adequate to
understand the dynamics of nanomaterials in the environment,
their interactions with target and non-target organisms, or
the occurrence of synergistic effe cts. These methodological
advances allow a life cycle assessment of the new developed
nanomaterials (
Kookana et al., 2014; Parisi et al., 2015). Besides,
studies on methodologies able to assess possible arise of
resistance mechanisms to nanomaterials by target organisms
should be undertaken. As a whole, the newly de veloped
analytical methodologies would support predictive models to
characterize, localize, a nd quantify engineered nanomaterials
in the environments. In this context, knowledge exchange
among scientists from different research fields would be essential
(Malysheva et al., 2015).
CONCLUSIONS
In conclusion, considering the great challenges we will be
facing, in particular due to a growing global population and
climate change, the application of nanotechnologies as well as
the introduction of nanomaterials in agriculture, potentially can
greatly contribute to address the issue of sustainability. In fact, the
efficient use of fertilizers and pesticides can be enhanced by t he
use of nanoscale carriers and compounds, reducing the amount
to be applied without impairing productivity. Nanotechnologies
can also have an impact on the reduction of waste, both
contributing to a more efficient production as well as to the
reuse of waste, while nanosensors technology can encourage the
diffusion of precision agriculture, for an efficient management of
resources, including energy (
FAO and WHO, 2013).
However, as with the application of all new technologies, there
is the need to perform a reliable risk-benefit assessment, as well as
a full cost accounting evaluation. I n the case of nanotechnologies,
this requires also th e development of reliable methods for
the characterization and quantification of nanomaterials in
different matrices and for the evaluation of their impact on
the environment (
Servin and White, 20 16) as well as on
human health (EFSA S cient ific Committee, 2011). Furthermore,
it is very important to engage all stakeholders, including non-
governmental and consumer associations, in an open dialogue
to acquire consumer acceptance and public support for this
technology.
AUTHOR CONTRIBUTIONS
All the authors participated in the drafting the manuscript and
discussion of all topics related to this perspective manuscript.
ACKNOWLEDGMENTS
The authors would like to thank São Paulo Science Foundation
(#2013-12322-2 and 2015/26189-8), CNPq and CAPES. Also
we would like to thanks Prof. H.B. Singh (Banaras Hindu
University–India) for his critics to this paper.
REFERENCES
Amenta, V., Aschberger, K., Arena, M., Bouwmeester, H., Moniz, F. B., Brandhoff,
P., et al. (201 5). Regulatory aspe cts of nanotechnology in the agri/feed/food
sector in EU and non-EU countries. Regul. Toxicol. Pharmacol. 73, 463–4 76.
doi: 10.1016/j.yrtph.2015.06.016
Aragay, G., Pons, J., Ros, J., and Merkoci, A. (2010). Aminopyrazole-based ligand
induces gold nanoparticle formation and remains available for heavy metal ions
sensing. A simple “mix and detect” approach. Langmuir 26, 10165–10170. doi:
10.1021/la100288s
Bellingham, B. K. (2011). Proximal soil sensing. Vadose Zone J. 10, 1342–1342. doi:
10.2136/vzj2011.0105br
Chen, H. D., and Yada, R. (2011). Nanotechnologies in agriculture: new tools
for sustainable development. Trends Food Sci. Technol. 22, 585–594. doi:
10.1016/j.tifs.2011.09.004
Dasgupta, N., Ranjan, S., Mundekkad, D., Ramalingam, C., Shanker, R., and
Kumar, A. (2015). Nanotechnology in agro-food: from field to plate. Food Res.
Int. 69, 381–400. doi: 10.1016/j.foodres.2015.01.005
de Medeiros, G. A., Arruda, F. B., Sakai, E., and Fujiwara, M. (2001). The
influence of crop canopy on evapotranspiration and crop coefficient of beans
Frontiers in Environmental Science | www.frontiersin.org 4 March 2016 | Volume 4 | Article 20
Fraceto et al. Applications of Nanotechnology in Agriculture
(Phaseolus vulgaris L.). Agric. Water Manage. 49, 211–224. doi: 10.1016/S0378-
3774(00)00150-5
De Oliveira, J. L., Campos, E. V. R., Bakshi, M., Abhilash, P. C., and Fraceto,
L. F. (2014). Application of nanotechnology for the encapsulation
of botanical insecticides for sustainable agriculture: prospects and
promises. Biotechnol. Adv. 32, 1550–1561. doi: 10.1016/j.biotechadv.2014.
10.010
EFSA Scientific Committee, (2011). Scientific Opinion on Guidance on the
risk assessment of the application of nanoscience and nanotechnologies
in the f ood and feed chain. EFSA J. 9:2140. doi: 10.2903/j.efsa.2011.
2140
El Beyrouthya, M., and El Azzi, D. (2014). Nanotechnologies: novel solutions
for sustainable agriculture. Adv. Crop Sci. Technol. 2:e118. doi: 10.4172/2329-
8863.1000e118
FAO, Food and Agriculture Organization of the United Nations and WHO, World
Health Organization, (2013). State of the Art on the Initiatives and Activities
Relevant to Risk Assessment and Risk Management of Nanotechnolog ies
in the Food and Agriculture Sectors. Technical Paper, FAO and
WHO, Rome.
Garnett, T., and Godfray, C. (2012). Sustainable Intensification in Agriculture.
Navigating a Course Through Competing Food System Priorities, Food Climate
Research Network and the Oxford Martin Programme on the Future of Food.
University of Oxford, UK
Grillo, R., Abhilash, P. C., and Fraceto, L. F. (2016). Nanotechnology applied to
bio-encapsulation of pesticides. J. Nanosci. Nanotechnol. 16, 1231–1234. doi:
10.1166/jnn.2016.12332
Grillo, R., Dos Santos, N. Z. P., Maruyama, C. R., Rosa, A. H., De Lima, R., and
Fraceto, L. F., et al. (2012). Poly(epsilon-caprolactone)nanocapsules as carrier
systems for herbicides: physico-chemical characterization and genotoxicity
evaluation. J. Hazard. Mater. 231, 1–9. doi: 10.1016/j.jhazmat.2012.
06.019
Kah, M., Machinski, P., Koerner, P., Tiede, K., Grillo, R., Fraceto, L. F., et al.
(2014). Analysing the fate of nanopesticides in soil and the applicability
of regulatory protocols using a polymer-based nanoformulation of atrazine.
Environ. Sci. Pollut. Res. Int. 21, 11699–11707. doi: 10.1007/s11356-014-
2523-6
Khin, M. M., Nair, A. S., Babu, V. J., Murugan, R., and Ramakrishna, S. (2012). A
review on nanomaterials for environmental remediation. Energy Environ. Sci.
5, 8075–8109. doi: 10.1039/c2ee21818f
Khot, L. R., Sankaran, S., Maja, J. M., Ehsani, R., and Schuster, E. W.
(2012). Applications of nanomaterials in agricultural production and crop
protection: a review. Crop Prot. 35, 64–70. doi: 10 .101 6 /j.cropro.2012 .
01.007
Kookana, R. S., Boxall, A. B., Reeves, P. T., Ashauer, R., Beulke, S ., Chaudhry,
Q., et al. (2014). Nanopesticides: guiding principles for regulatory evaluation
of environmental risks. J. Agric. Food Chem. 62, 4227–4 24 0. doi: 10.1021 /j f50
0232f
Lambreva, M. D., Lavecchia, T., Tyystjärvi, E., Antal, T. K., Orlanducci,
S., Margonelli, A., et al. (2015). Potential of carbon nanotubes in
algal biotechnology. Photosyn. Res. 125, 451–471. doi: 10.1007/s11120-015-
0168-z
Liu, R. Q., and Lal, R. (2015). Potentials of engineered nanoparticles as fertilizers
for increasing agronomic productions. Sci. Total Environ. 514, 131–139. doi:
10.1016/j.scitotenv.2015.01.104
Ma, X., Geiser-Lee, J., Deng, Y., and Kolmakov, A. (2010). Interactions
between engineered nanoparticles (ENPs) and plants: phytotoxicity,
uptake and accumulation. Sci. Total Environ. 408, 3053–3061. doi:
10.1016/j.scitotenv.2010.03.031
Malysheva, A., Lombi, E., and Voelcker, N. H. (2015). Bridging the divide between
human and environmental nanotoxicology. Nat. Nanotechnol. 10, 835–844. doi:
10.1038/nnano.2015.224
Mishra, S., and Singh, H. B. (2015). Biosynthesized silver nanoparticles as a
nanoweapon against phytopathogens: exploring their scope and potential in
agriculture. Appl. Microbiol. Biotechnol. 99, 1097–1107 doi: 10.100 7/s 00 2 53 -
014-6296-0
Mousavi, S. R., and Rezaei, M. (2011). Nanotechnology in agriculture and food
production. J. Appl. Environ. Biol. Sci. 1, 414–419.
Nuruzzaman, M., Rahman, M. M., Liu, Y., and Naidu, R. (2016).
Nanoencapsulation, nano-guard for pesticides: a new window for safe
application. J. Agric. Food Chem. 64, 1447– 14 83. doi: 10.1021/acs.jafc.
5b05214
Oliveira, H. C., Stolf-Moreira, R., Martinez, C. B. R., Grillo, R., De Jesus, M. B.,
and Fraceto, L. F. (2015a). Nanoencapsulation enhances the post-emergence
herbicidal activity of atrazine against mustard plants. PLoS ONE 10:e01329 7 1.
doi: 10.1371/journal.pone.0132971
Oliveira, H. C., Stolf-Moreira, R., Martinez, C. B. R., Sousa, G. F. M., Grillo, R.,
De Jesus, M. B., et al. (2015b). Evaluation of the side effects of poly(epsilon-
caprolactone) nanocapsules containing atrazine toward maize plants. Front.
Chem. 3:61. doi: 10.3389/fchem.2015.00061
Parisi, C., Vigani, M., and Rodriguez- Cerezo, E. (2015). Agricultural
nanotechnologies: what are the current possibilities? Nano Today 10, 124–127.
doi: 10.1016/j.nantod.2014.09.009
The Royal Society (2009). Reaping the Benefits: Science and the
Sustainable Intensification of Global Agriculture, London: The Royal
Society.
Sadik, O. A., Du, N., Kariuki, V., Okello, V., and Bushlyar, V. (2014). Current and
emerging technologies for the characterization of nanomaterials. ACS Sustain.
Chem. Eng. 2, 1707–1716. doi: 10.1021/sc500175v
Scognamiglio, V. (2013). Nanotechnology in glucose monitoring: advances
and challenges in the last 10 years. Biosens. Bioelectron. 47, 12–25. doi:
10.1016/j.bios.2013.02.043
Scognamiglio, V., Arduini, F., Palleschi, G., and Rea, G. (2014). Biosensing
technology for su stainable food safety. Trac-Trends Anal. Chem. 62, 1–10. doi:
10.1016/j.trac.2014.07.007
Sekhon, B. S. (2014). Nanotechnology in agri-food production: an
overview. Nanotechnol. Sci. Appl. 7, 31–53. doi: 10.2147/NSA.
S39406
Servin, A. D., and White, J. C. (2016). Nanotechnology in agriculture: next steps
for understanding engineered nanoparticle exposure and risk. NanoImpact 1,
9–12. doi: 10.1016/j.impact.2015.12.002
Valdes, M. G., Gonzalez, A. C. V., Calzon, J. A. G., and Diaz-Garcia, M. E. (2009).
Analytical nanotechnology for food analysis. Microchimica Acta 166, 1–19. doi:
10.1007/s00604-009-0165-z
Vanderroost, M., Ragaert, P., Devlieghere, F., and De Meulenaer, B. (2014).
Intelligent food packaging: the next generation. Trends Food Sci. Technol. 39,
47–62. doi: 10.1016/j.tifs.2014.06.00 9
Yao, J., Yang, M., and Duan, Y. X. (2014). Chemistry, biology, and medicine of
fluorescent nanomaterials and related systems: new insights into biosensing,
bioimaging, genomics, diagnostics, and therapy. Chem. Rev. 114, 6130–6178.
doi: 10.1021/cr200359p
Conflict of Interest Statement: The authors declare that the research was
conducted in the absence of any commercial or financial relationships that could
be construed as a potential conflict of interest.
Copyright © 2016 Fraceto, Grillo, de Medeiros, Scognamiglio, Rea and Bartolucci.
This is an open-access article distributed under the terms of the Creative Commons
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